Companion Pet Clinic - Klamath Falls, CA - (541) 882-7674
Both cats and dogs very reasonable priced and can get you in relatively quickly. View prices.
SNYP-Talent, Oregon - Cats Only. They also have feral program https://spayneuter.org/
Scott Valley Vet - Fort Jones - (530) 468-5366. Prices are very reasonable
Purr Angels - (530) 842-1875 - Feral Cats Only
SNIP - Assistance Program - request a coupon toward your spay and neuter of cats and dogs. Must income qualify and have a vet appointment already scheduled.
Rescue Ranch Alter Assist Program - (530) 859-0139