Most RV parks will charge a $10-$20 fee for an outsider to dump. Sometimes it's just worth it to spend a night. If you can find a wastewater treatment plant many times they'll allow you to dump.
Hopefully, you can find a place as you travel if not in the immediate area. Where are you heading?
Full-timed for 16 Years . . .
Traveled 8 yr in a 2004 Newmar Dutch Star 40' Diesel
& 8 yr in a 33' Travel Supreme 5th wheel