In Way Beyond Monochrome, Ralph Lambrecht's and Chris Woodhouse' new book (a beauty, by the way), some magnetic frames are discussed. They have a magnetic backing, and over frame, with glazing. They come apart and go back together and sound like a nice solution to exhibition, just changing out the print.
Is there a US source for these?
A Google search turns up a web site which seems to be more about instant film products.