Help Bubba recover and live a long life

Bubba is a sweet boy who showed up at our house at the end of July. He had no microchip and after posting on numerous lost pet pages, no owner came forward. We had him trapped and fixed and have assumed care for him. He was very skinny and ragged when he showed up but has really developed into a loving, adorable, and handsome fellow. He is currently indoor/outdoor but we have been working on making him permanently indoor. Yesterday, he stopped eating and developed bloody diarrhea. He was eating 5 to 6 cans a day before this. He is currently at the urgent care vet but they are saying he needs to go to a 24 hr emergency vet for additional care. He also tested positive for FIV. We are already looking at a $2500 visit plus a possible $4000 additional charge from the emergency vet. Any help would be greatly appreciated. We feel that Bubba deserves this chance. Thank you