I just bought a Sparco EVO 2 (US) seat with matching bottom-mount rails and hardware from Amazon. You gotta love Prime!
For now, I'm just going to run a single seat. The car is already corner-weight balanced with me in the driver's seat, so it won't be too far off (though I get to go through this again when I change out my coilover setup, again!).
If this goes in nicely, I'll probably add a matching seat down the road. I'm jazzed about the weight savings here!
Also, my front Recaro and rear seats have been sold. Congrats, DBS!