The only litmus paper strips I can find online either aren't sensitive enough to test the pH down to the decimal or they start too high, at 5.5, since they're meant to be used for urine and/or saliva. Since vaginal pH shouldn't be higher than 4.5 this is obviously no good.

I know Vagisil sells a testing kit, but buying that will get expensive after a while. I would like to be able to test myself whenever I want, at home, for not much money.