'True Faith' evokes the same sort of rarity as 'True Love', or 'True Hope', etc.. It is not synonymous with holiness. Holy objects and symbols seem to far, far more common than the Ideal Truths (yes, I just made that term up, but I like it for encapsulating what I've so far been referring to as the 'True [X]'s).
Holy water is available relatively easily, from what we've seen in the fiction, if you just know the right places to get it.
Ideal Truths, on the other hand, have no established mechanism to even confirm whether a suspected symbol of one will function short of using it on something that's known to be vulnerable (and remember that even the WCVs, the only significant example from the fiction, did not have their weakness known to the White Council, a substantial rival that stands or falls substantially on the basis of its intelligence gathering ability; mechanically, it was a +0 Catch with respect to the availability of the knowledge).