Racing seat with lower back support?

So as much as I enjoy driving my S13 a longer drive (30min or so) starts wreaking havoc on my lower back. I'd like to swap in a more supportive seat that won't kill my back that fast. Is there such a seat out there?
BTW the S13 seats are side mount, so no altima/sentra/200sx/G20 seats will work.

I fold up cloth/padding and usually put it behind the removable back pads for a makeshift lumbar support. Has worked well for me.

Ugh. I had a beat-to-hell S13 as my first car and the seats doubled as torture devices. The S13's goofy seat rails limit seating options, unfortunately.

http://forums.nicoclub.com/alternate-seat-options-t162671.html

From this thread, it sounds like S14, S15, and R32 GT-R seats fit without or with little modification. The first guy mentioned Nissan Frontier seats, but no details as to whether or not they fit without modifying the seat rail. I found the how-to they mentioned on modifying 350Z seats to fit:

http://zilvia.net/f/tech-talk/140658-z33-seats-into-s-chassis-how-diy.html

The S14 and Frontier options sound the cheapest, the R32 sounds the best for motorsports.

Get a McKenzie Lumbar Roll if you want to be balla : http://www.amazon.com/Original-McKenzie-D-Section-700-Lumbar/dp/B000GPM520/ref=pd_sim_ba_4

It has velcro on the reverse side and will stick to the fabric on your seat. i have one on my Cobra Monacos (very flat) and it helps a lot.

The best solution I've found is a pump-up inflatable lumbar; it inserts between the seat frame and the foam. About $30 and they are worth every penny. I put it in my Focus seat - all I had to do was slide it in, didn't remove anything. Took 5 minutes.

It was such an improvement I put another one in my Sparco Pro2000 racing seat.

interesting idea on the aftermarket lumbar support.
I will be looking into the frontier seat idea. S14/5 seats I knew, but from my looking it is cheaper to buy knock off ebay seats than them.
Just have to keep searching i guess

I vote inflatable lumbar. I've had them in every Miata that I've owned, just slide them out when I sell, and slide them in the next one.