Marc,
Probably the best bet for an LMI Lambda emulator is Daniel Seagrave's LD
GitHub project. See:
https://github.com/dseagrav/ld
It has directions on where to get the LMI code (bitsavers) and how to set
up the emulator. I use it quite a bit and it works quite well.
Of course, it has mappings to a regular keyboard, not the LMI keyboard-- so
you would have to create an interface and then change the LD code. Did find
this link to a possible USB interface:
https://web.archive.org/web/20150910154424/http://home.comcast.net/~mmcm/kb…
The LispM mailing list might be a helpful source of information:
http://lists.tunes.org/mailman/listinfo/lispm
Mike