Sweetie, I think your best bet would be to pay for veterinary euthanization. All of the ways that I can think of of home euth for reptiles are either too slow or painful to be effective, and the only quick painless way of I can thinkis also the most violent on the part of the handler. Not for the weak of heart or stomach. I'd research your vet's methods of euthanization before confirming though. You love him so much, he deserves the best possible way to go.
Let us know what you decide.