It seems to me you have 3 options:
- Replace / upgrade your hubs and brake rotors to a 5 lug in front and new axles and rotors in the rear. You may be able to have them re-drilled by a machine shop, but that's likely not going to be much less money than just replacing them.
- Locate a set of 4 lug wheels - likely custom.
- Use 5 lug wheels with adapters. You'd most likely need different offsets on the wheels to compensate for adapter thickness.
These options are presented in most-favoured to least-favoured order.
Just my $0.02.