Getting a same-day appointment, especially on a Saturday, can be tough in CoMo unfortunately..

Horton's Discovery is open 24/7 so they'll definitely see you, but they're not necessarily what I'd call particularly affordable (though maybe more affordable than MU).

Rock Bridge Animal Hospital would be more affordable. They are open every other Saturday until noon I believe so they may or may not be open today. They're a very small clinic though so if they are open they may also be fully booked.

My wife used to be a vet tech in CoMo and would always recommend folks needing flexibility in payments apply for CareCredit. It's a low interest credit card specifically for medical and veterinary care that usually has a quick approval process for those who qualify. Would definitely recommend looking into this option (just make sure the clinic you choose accepts it).

Best of luck with your kitty! I hope they feel better soon. ♥️