I was on a similar quest for a polaroid back for my horseman VH, which is 6x9cm, and I eventually concluded that putting on a 4x5 enlarging back with ground glass is a very good way to go. Then you can use any old 4x5 polaroid holder.
It would also be possible to adapt a 3.25" polaroid back from something like an rb67 for your purposes; that would involve a little engineering. But at least those backs are inexpensive.
yes - I would take photoes of my work, posting the whole set as a separate thread, if you want to see the result? It's very simple to do, and the result is very good.
Hmmm. I have extra rb67 backs.... I have the tools to attempt this. Got pictures? A 105 lens with a 6x4.5 rb67 back sounds like a nice medium telephoto set up.
yes - I would take photoes of my work, posting the whole set as a separate thread, if you want to see the result? It's very simple to do, and the result is very good.