Mount it on the carrier backwards and space out the rubber bumpers to rest against the tire that way. Longer bolts and spacers can be made out of just about anything. Wood, hockey pucks, etc.
A fellow club member has his spare on a stock wheel mounted on his carrier backwards on his YJ.
Or replace stock rubber tire bumpers with shorter cut pieces of wood or hockey pucks. I would not cut the stock ones, you may just need them later.
Or an aftermarket spare wheel with different backspacing.
Just some things to try.