Not many 90* were made for the LED, wouldn't be cheap.
IMO you should do what I did. Use a rechargeable 9.6v and run your harness through the bottom of the grips - then you go to radioshack and grab one of those little black ABS 9v cases and drill two holes in the edge of it. Stick the edge in between your marker and ASA, slide the mounting bolts through the holes, et voila.
I wanna say it cost me $20 and 20 minutes circa 1999.