Sometimes words can mean more than any tangible item. Have you thought about writing him a letter expressing everything positive (no negatives) about him, and how much you really enjoy having your 'dad' back? It may be that on his bad days, a letter like that could be reread as a reminder of why he shouldn't go back to drinking.
If nothing else, he'll have a permanent reminder of having a daughter who loves him. Pretty hard to find something greater than love to give to a person.