4WD Hardware sells all the parts for the front D30 axle disconnect. Before buying parts, I'd try to nail down the problem. On one of my old YJ's, the front axle disconnect stopped working because battery acid got on the vacuum line and put a hole in it. I'd start by testing the disconnect motor manually using a vacuum pump or a manual pump (your mouth, it works
). Anyway, if I were to guess, I'd put my money on a vacuum leak somewhere in the system. There is also the possibility that everything is fine and it is only the light not working. Have you tried putting it in four wheel drive and doing tight turns on pavement to see if it is engaging or not?