I'm done, but when the next detail rolls around, can I use anything in place of the clay lube? Do they sell clay lube alone?

Yup, just look for Meguiar's Quick Detailer or Mother's Showtime Instant Shine. If you want, you can also mix some water with car wash soap and that works fine too.

Awesome! Any recommended proportions for the carwash soap/water route?

I clayed my 99 this weekend. Used the hose on low, kept everything wet, worked fine. The detailer, or water with some soap in it , serves as a lubricant with minimal detergent property. The main issue is the clay will not work without lubrication.
I also found using the hose to be much quicker than pumping that spray bottle for 30 minutes. Less tiring on the left hand also.

I use water and a couple drops of dishwashing liquid soap in a spray bottle