Do you have dogs or cats or other animals or is he outside at all? Coccidia doesn't just appear spontaneously in an older squirrel like this.
Baycox - torturazil - is very good for coccidia if the answer to the above is yes. Looks like this place:
https://www.allthingsbunnies.com/Tol...s-p/med132.htm has it mixed up for bunnies which would be good for a squirrel. Note that they are also in Colorado so you may be able to get it quickly.
What does he eat? What was he eating before the problems started?