As far as I know, AZ Spectrum is the sole entity alive today that has had a history servicing the GSMO. Ian Love, one of the main engineers of the GSMO (which has absolutely no interchangeable parts with the CP-16 et. al) hasn't been able to be reached in awhile -- he was at some point (we're talking like 2006) able to service GSMOs in the UK.
There are a few 400ft GSMO magazines for sale located in CA on eBay. Out of curiosity, I asked the person selling those magazines if they had any fully working GSMOs, they told me they have little bits and pieces laying around. I'm fairly new here and not sure if I am allowed to attach external links, but I hope you can find the listing (it's the only actual GSMO related object apart from instruction manuals that show up for the query "GSMO") and reach out to them. Good luck.