If you are a resident of Fidalgo or Guemes Islands and need help with your cat's medical expenses, the Anacortes Animal Relief Fund (AARF) may be able to help. Call AARF at (360) 293-2865.
SPOT also has a fund to help with emergency medical expenses. See their website for more information.
Prices can vary widely from clinic to clinic so you might also shop around to find a vet that will work within your budget.
If you're facing a large expense, CareCredit offers financing for veterinary expenses.