You could just bring everything in powder form. D-76 or XTOL, and Kodak (and others) sell fixer in powder form too (e.g. https://www.bhphotovideo.com/c/produ...xoCgBEQAvD_BwE).

Bring some empty accordion bottles which pack nicely and maybe the SP-810 or at least a tray and a foam core board.

Not sure where you’re going to spend the night but assuming you are staying in a motel or somewhere with a bathroom, you could also bring black cloth and tape, to seal around a bathroom window… and develop at night.