I just read your post and am intrigued by the last comment about getting an HP 9153A working with an MFMulator. What would be involved in achieving that? I have a 9153B that needs a replacement hard drive and would be interested in a solid-state solution if there is one.
As far as I know, it’d just be a matter of replacing the MFM drive in the system with an MFMulator: http://www.pdp8online.com/mfm/