I saw lots of these things in the past few weeks so I just did a quick search of the big auction site here in Germany (I'm assuming that Mark is talking about Eb**y. Of course, they have been snapped up. I do have the current replacement part price list from Leica that lists at 24x26mm negative holder, while it isn't the exact size you are looking for but maybe it is close enough, and when not then try to write the contact number and ask. If you are interested please let me know, I have it saved as a pdf. and would need to e-mail it to you. I don't have a link for it sorry. Might work. Good luck!