While you're awaiting your RO/DI unit, go for the distilled water (not the plain RO) if you can find some. I'd imagine you'll get a lower TDS from distilled (really it should be zero if it's distilled I'd think) over just RO.
Bottled drinking water is going to be very expensive, and if I recall correctly, most of it is just tap water with a label on it
If that is your only option, I'd just hold out for an RO/DI unit if possible.