Your options are limited when it comes to 2 shot panoramas and DSLR cameras especially small DX/APS-C sensor DSLR's.
Basically you can choose from the Sigma 4.5mm Fisheye or Sunex Superfisheye if you want to buy something under $1000. Over this amount you can run with the Coastal Optics fisheye at $4000+
None of these will yield super results with two shots as the overlap is small (very small) and will make for difficult stitching and show to some degree dark lines because of vignetting at the seams.
You would be far better of shooting 3 shots at 120 degrees or 4 shots at 90 degrees. There are many reasons why this would be better.
- Lots of overlap for stitching control points.
- Fisheye images are typically softer at the edges with the centre part of the image sharpest.
- Software support.
- Forum/User support.
Personally I would suggest you shoot with a Sigma 8mm fisheye (4 Shots, 4+T or 4+TB) or use a Nikkor 10.5mm Fisheye (6+TB).
I don't believe you will ever be happy with any of the two shot options in the long run.