Was this Model M from grubb3r5 on ebay? If so i was watching that M because I needed some parts to fix another M I have.
AS for controller compatiblility, I own very early to very late 1391401's and all have interchangable membrane traces. However if you are getting parts from Blue label Lexmarks, the LED and bottom trace are combined but to utilise this kind of trace, get a exacto knife and cut where the two traces join but carefully. Controllers are all compatible in the 1391401 range. Where to get parts, try clickykeyboards.com. Brandon has lots of unlisted parts, ask him if he has any. If you are in Sydney, try going to Reverse Garbage. I have not personally been there but from the photo of the ewaste they collect, it may be a good place to look for Model M's.