From the top of my head:
- a whip
Great as a focus for sonic based evocation, since a whip actually does a supersonic boom when used right.
- gloves
Depending on the kind of gloves, they might even offer some protection or weaponry. There are some out there filled with quartz sand over the back of your hand, which would be perfect for this sort of thing. You can fill it with enchanted sand or just cover it in runes or whatever narrative might fit your practitioner.
-gloves 2.0
Do you remember Pyro from X-men? He could only control fire, not create it, so he build a glove that would pull the lever on a lighter if he moved his arm the right way, so he could create and control the fire with one move. You could do something similar as a fire focus, a glove that creates a tiny flame with a tiny effort of will. Now that doesn't actually cost you an action, it's just the narrative, that you can do more powerful fire evocations, since you only have to control the fire, not call it up, when using the glove.
- brass knuckles
Like rings but 20% more ouch on mundane fighting. Kind of boring though, I think.
- A frisbee
Can be great as a kinetic attack focus. You make a movement as if you throw the frisbee, but instead of releasing it, you release a disc of kinetic energy instead that flies at your target. Could do the same with a ball or boomerang or similar things.
- glasses
A focus for cyclops style laser beams would be the first choice, but a lot of spirit evocations would fit as well. A science-magic character of mine even has a single lens as a focus for optical evocation.
- A pouch with a pulverized mixture of sulfur and ashes (and maybe some other stuff)
You can use the powder for multiple things. First, you prepare it like you would any focus item, that takes a good amount of time, more than just grinding up the ingredients and mixing them up. You need to get the ashes from coal you burned on the full moon or something like that. Regardless, for all intents and purposes, the pouch with the powder is your focus item. But of course you could use the powder itself to make mundane maneuvers, throwing a hand full of the powder at your foes and then igniting it, using the tag to increase your attack. After that you could say you have enough powder in your car or in your lab to refill, or you selfcompel to remove your focus item.
- a phoenix feather
Nothing much to say. Acquiring one might be tricky, but it should be one of THE best fire focus items around. If your wizard has one, there should definitely be a story behind it.
- replaced bodyparts
This might not be for the squeamish, but it is definitely an option. Depending on the wizards state of mind, he might have removed the bodypart in question himself (warlock?!), or it might have been an accident or wounds from various battles. A glass eye would be an example. Another one would be from a friend of mine. He is missing the front two segments of his right index finger. I could see a focus item like a wooden replacement that is attached with strips of leather around the wrist. For attack spells, it is literally point and shoot.
- branding iron
It symbolizes fire fairly well I think. Though it might be too close to the staff and rod you are trying to avoid. On the plus side, it doubles as cold iron in an already weaponized way. And throwing a branding through the air is all kinds of cool. Hmm, I think I need to create a new character just for this.
- a cape
Kind of like Bianca's dress of fire in GP. A red cape that transforms when you draw upon it's power, engulfing you in cold flames.
- bottle of water
That's right, simple as that. Well, maybe not. It should be a pretty sturdy bottle. Thick plexiglas for example. Then you'd need some special water, which would be the actual focus. Water from a special well. Or from one of those geysers somewhere. Maybe you get some special water in a bargain with a water elemental. (ok, maybe better for water than for yours, but while we're at it
)
Would work for fire if you filled it with some kind of flammable liquid and have an atomizer on top. In that case, the bottle is enchanted and transfers its properties to the liquid when it is sprayed out.
Of course you'll always have to think about the size restrictions if you want to put a lot of focus item slots on one item. If those above aren't to your liking, you should tell us a bit more about your character, so we can better see what might fit his style.