While I have an MR8100 I *will* admit that It has been a fairly long while that I've actually looked at, let alone used, it so I don't quite remember just what the connector(s) look like. But, you might try checking what MCM Electronics (
MCM Electronics: Home and Pro Audio/Video, Security and Test Equipment) might have. If they don't they might have something you might find useable for making up your own wiring. (Yes! I do know that finding the correct connector is a more `comforting' situation. But, *if* you really have to get the radio back in service sometimes it is not a bad thing to do as long as you take steps to at least preserve enough of the original wiring and connector to be able to restore it, if or when, you finally come across what is needed to do said restoration and get it working that way.)
Having made that, possibly blasphemous, suggestion your question *has* somewhat piqued me into actually considering going and ransacking my "Bide-A-Wee Home for Orphaned and Superannuated Scanners, Computers, and other Miscellaneous Electronics" storage `cavern' to try and find my MR8100 and see if it may be possible to find it *and* find a current use I can put it to. {WAN GRIN!} *If* I do find it, it may take a while, I *will* try to remember this thread and let you know what type connector it uses and some possible places you can acquire the bits-n-pieces to make up a more fitting cable. Hopefully we will both get `lucky' and someone will happen along with the necessary info? However, you now have, thank you very much, as I have said piqued my interest and jogged some fond memories of my prior useage of said radio enough that now I have to dig it out and try and find a place to set it up and play with it again. {VB GRIN!} It was my first scanner that had an alphanumeric display and I remember how nice it was back then to actually see who one was listening to rather than just what frequency it had chanced to stop on.