I will second the idea (or third it maybe with two previous posts
) about a Kirkey seat. I use an UltraShield race seat and they are very similar and fit about the same, but the US seat was cheaper so I went with it. They are both good aluminum seats and the belts will be close enough together over the shoulder to hold the HANS brand restraint. and they are offered in a wide variety of dimensions for no extra charge - in fact I think US doesn't charge extra for custom sizing, you just have to wait a few weeks for them to be built v. off the shelf. I got lucky all my dims matched an OTS item so I got them immediately.
That said I have an R3 and prefer it over the Hans - I tried a friends HANS and it fit fine, but I like the fact I can go to a regular belted car for a ride along, or a 4pt car, whatever and have neck restraint. And the price was right too - on the bird board a guy named Chad Plavan is a dealer for them.
In any event, if you have a HANS, tell the mfr you have one as sometimes they have a special seat design to work with them (extra relief right behind the neck for the device).