Help Mouse Fight FIP

hello! i adopted mouse from a rescue in 2020, after moving out on my own for the first time. he's now a little over 4 years old and struggling with illness.

mouse has a 5x7cm mass and a lot of fluid in his abdomen that just keeps building up. he's gotten much skinnier everywhere except his belly, because of all the fluid. his vet suspects FIP, or feline infectious peritonitis, a mutated form of the feline coronavirus. unfortunately, FIP is commonly diagnosed by excluding all other differential diagnoses, as there is no definitive test for FIP.

until recently, FIP was a fatal disease. however, as of june 2024, veterinarians can now prescribe an oral pill to treat FIP! this is much less stressful and painful than the injections i have been giving him. the only downside is cost - at his current weight, a full 12 weeks of treatment (the mandatory duration) is quoted at $1391. this figure can and likely will go up as his weight increases, as the dose must be increased accordingly. that quote also doesn't account for supplies, such as needles and syringes (which are necessary to give him injections until his GI tract is stable enough to absorb the pill form), or diagnostics, which have already cost me $1110.

i need help to treat him. it will take me months to pay off just his diagnostics, which is what this gfm is for. please help us make this a bit easier.