Well, to be fair, the example for a +0 for availability is a Sword of the Cross, which are hard to come up with on the spur of the moment also.  I was under the impression that availability and knowledge are really supposed to be separate requirements.

I think the stereo trick should work.  Similarly, I imagine he could use a (battery-powered) computer inside a circle with one of those laser virtual keyboard things projecting out of it.  Or he could set up a projector/camera thingie inside a circle, and use a system similar to SixthSense, only bigger.  For internet, I'm thinking 4G wireless would be the best bet...

I've spent way too much time thinking about this.

* puts on the GM cap my players made me for these specific situations *

If you could explain in real-life physics how to use fire to burn away the oxygen around a persons face without causing second and third degree burns, or worse, then sure, but I can't think of anyway you could do that. Also, there is a looooot of difference between fire and microwaves. That is why the pain gun you mention is controversial and trying to do the same thing with a flame-thrower is not even considered an option.

Well, since we're (presumably) not playing a game about physicists who fight vampires by night, how about I throw out some magi/techno-babble patter and you tell me if it sounds plausible enough to work for Harry?

1. Fire magic grants some ability to control heat flows generally.  An example can be seen from the case where Harry makes a big gout of flame, taking the heat from Lake Michigan in order to freeze a portion of it to run across.  Depending on level of control*, a mage could create fires in the vicinity of a target, but pull enough heat away from the target not to cause lethal burns.

2. As far as I understand it, the microwave gun works on the same basic principle as a microwave oven, you hit water and fat molecules with microwaves, exciting them, causing heat.  Now, in the gun, the heating is supposed to be limited to the outermost part of the skin, decreasing the amount of long term tissue damage.  Again, with sufficient control*, you should be able to use fire magic to create a similar effect.  Also, we may be more willing than the army to see some tissue damage, so long as it isn't lethal.

However, I would like to restate that even without explicitly "less-than-lethal" evocations, I think it should be possible for reasonably creative players to come up with plausible "taken out" results that don't involve killing.

*For the purposes of this discussion, I think it's safe to assume pretty solid control, since here we're talking about evokers who are getting +8 or +10 on their control rolls.

After some sessions of play and similar situations I'm with luminos on this one. If you don't want to kill your opponent, then don't hit it with heavy duty stuff, because it is bound to kill someone some day. It is a question of relations. If a Evocation Attack Action is designed to be Weapon: 5 it should be comparable to any other Attack with a Weapon: 5. There is a reason why the wizards of the books only use their aggressive magic (excluding enchanted items like the force rings) when they truly want to hurt some. It's because it is potentially lethal to do so.

I don't know, from my reading of the mechanics, there's nothing saying that you have to kill someone when you "take them out" with a shotgun either.  You always get to dictate the outcome, maybe they pass out from blood loss or shock, maybe they're paralyzed, maybe they're lying on the ground groaning, conscious, but only capable of crawling away.  Perhaps they are largely uninjured, and merely have to retreat under fire, neutralizing them as a threat long enough for you to get away clean.  In a sword duel, you could narrate that they are disarmed, and you have your blade at their throat, drawing a single drop of blood.  It seems to me that you have a great deal of freedom here.

When it comes to evocation specifically, I would imagine that you have even greater freedom.  You use electricity to "taze" somebody, air to sleeper-hold them into unconsciousness, earth to leave them in the bottom of pit, spirit to put them in a trance, etc.  The only real requirement is that your "taken out" result makes narrative sense, which shouldn't be too hard assuming a certain degree of player creativity.

If you just want incapacitate someone or show somebody who he is up against use other types of actions. Make it a maneuver. A good example is Elaines Mind Fog (YW 299). There are other examples in the book. In my opinion maneuvers are the way to go if you just want to knock somebody unconscious via magic.

Maneuvers are only going to apply aspects, right?  I mean, you could try a compel for them to go to sleep, but that probably won't work against anybody important enough to have fate points, at least not in a combat situation.