Your local trailer shop might be able to custom make or adapt one for you. Or my trailer guy Eddie English in Milton, Florida makes them on site, sends them off for galvanizing, then assembles them with whatever you want. He does aluminum as well but galvanized will probably run $1500-1800 depending on tire size, fenders, spare, LED lights etc...
https://www.facebook.com/eddieenglishcompany?fref=ts