Huge bladder stone bleeding stray male cat vet bills

We had a daily visitor at the shelter, he would mark, pee and bleed on the bedding. Finally I caught him after 1 month for spaying, but it turns out he had a huge bladder stone, causing wounds and infection in his urinary sustem. It was so big, 1cm, that the vets had to remove it surgically. Lucky guy I would say, now he is free of pain and out of infection danger! Unfortunately I cannot cover the cost of such an operation, as I care for the shelter and all its expenses. This poor stray needs donations to help him pay his bills. If I am forced to pay it once again I will not do another rescue. I have already too many pending vet bills and unpaid stray cat neuterings. I feed over 30 cats on a daily basis and maintain 12 litter boxes. I simply cannot afford anything more... If you care to help out, donate the value of an afternoon coffee and cake, you are missing out now with the lockdowns and help me, help more strays. I attach the invoice.