HP 9845 Option ROMs

So in the past few weeks I've been playing with my latest aquisition, an HP 9845A that's been upgraded at some point to a 9845B. The filter caps for the PSU are in the mail still and I have yet to actually see the system turn on so I've been working on other projects in the meantime like cleaning the machine, troubleshooting faults in the floppy drives it came with and sourcing a food dehydrator to bake the tapes it unexpectedly came with. It's a fairly basic machine without the internal printer or second tape drive. Only the I/O, graphics and Mass Storage ROMs are installed and there's at least one other option ROM module not accounted for according to one of the manuals that came with. In fact it seems the option ROMs aren't common to begin with or at least they are not cheap on ebay. I seem to remember a few years ago someone out further West than I am who also had a 45 discussed some sort of ROM board that acted like the PRM-85 ROM board for the HP 85 and let you load whatever ROMs you wanted onto a modern EPROM and do away with HP's silly modules completely however my memory is fuzzy and I can't seem to find any mention of such a device on the internet. What I did find was the System ROM replacement board on hp9845.net but it doesn't mention the ability to add in images of the option ROMs he has available on his site. Anyone else heard of this mysterious adapter? -John