Agree on LFS being a good, relatively cheap source depending on the size of your tank and your water needs per week.
If you don't want to go through the (minor-ish) hassle of adapting it to a 5/8 hose bib, then I'd go LFS if it's temporary. If you need cheap water jugs, Menards sells 4 gallons full of RO (not RODI) for around 5 or 6 bucks. I just use those jugs. Not a great size at 4 gallon, but way cheaper than the 16 dollar walmart ones because no deposit. The Menards ones are green and at the front of the store, usually right next to the exit inside.
I believe supermarket is usually RO, but not DI. Phosphates and such can be a problem here without the DI stage. Someone else can correct me here if I'm wrong, but that's what I've heard. Those last 10 or so PPM that the DI takes out can cause problems.