Welcome, Tonya! Our local Walmart seems to run out of distilled water quite regularly. But if I go to the baby section, I often find a gallon or two, tucked away by the bottles and powdered formula. It's the same stuff, for the same price; it just has a cute baby on the front label.
I've also used AVJ and plain white vinegar for water. The AVJ is a one-to-one sub for distilled water, but it's pricey. The vinegar is much cheaper, but it requires some extra calculations to adjust the amount of lye. The SoapmakingFriend calculator will do that for you, if you do all of the following:
1. Under
Custom Additives, select
Vinegar (commercial 5%)
2. Mark
Yes to
Liquid Discount? - which is under the spot where vinegar is now listed
3. Tinker with the amount of vinegar you are adding (still under
Custom Additives) until you see that the amount of additional water needed (under
Results) is as close to zero as you are able to get it. This will depend on your batch size, etc. Also, note that this doesn't work if you are using master-batched lye solution. Then you have to do the math on your own, which is explained here:
Acetic acid (Vinegar) | Soapy Stuff
It's a bit of a fiddly process in the calculator, but vinegar does help your soap to unmold more quickly, and adds a nice lather feel, IMO.
Good luck, and welcome to SMF!