Snapped bolt...

I guess I over tightened the bolt when I took the seat apart a month ago? I am about to take the seat apart again for foamectomy, but the bolt that attaches the seat back to the base on transmission side of the seat is snapped. The head came off and the shaft is still threaded in. Now what do I do? I'm going to MSR next weekend...

How do I get it out and how do I get a replacement? It's kind of a weird bolt...

Whatever you do, DO NOT use the bolt extractor to get the stuck bolt out! I spent 2 hours this morning using a diamond bit and making little progress in taking the broken extractor out. I may have to take it to have someone weld a stock to the broken bolt to take the bolt out.