It struck me this AM that 914 seat belts in good condition seem to be a bit spendy but 944 stuff is cheap (and newer).
Any reason not to use a 944 set up? I think the mounting point bolts etc are all interchangeable. Only issue I can see is physically where they mount is different and the belt length may not be compatible but I've not tried it.
Awaiting a dope slap if this is a terrible idea.