Easy solution is to buy a divers seat Mate, and a drivers seat base, that's what I did.
It just means that the controls are on the wrong side, but it's workable and costs a fraction of what single passenger seats cost.
They will both fit without any mods apart from cutting the carpet, as the holes are all there, you can even use the existing bolts.
It also means that you can fit you battery easily, although I have two batteries under my driver' seat so use the space under passenger's for fire extinguisher and junk.
I was really lucky in that I got a heated one with a pump up back out of an AA van, so I put that on my side and my old one on passenger side.
Also managed to get a single seat door card with an arm rest, which fits nicely up against the existing arm rest. It does mean that the existing arm rest is on wrong side but that doesn't really cause to many issues, and I've built a centre console/arm rest so that passenger has something in middle to rest on, and I have more room to store junk
