I may not know much about the prop suits, but I'll chime in with what I know about what this was based on. This suit is obviously stylized after the Apollo A7L suits used from missions Apollo 7 to Apollo 14. The crotch region on the Apollo 15 thru 17 suits was different to allow better bending down there to fit in the lunar rover seats (and the chest connectors had a more asymetrical pattern). The suits used in Apollos 11 and 12 did not have red stripes on the commander (those were added for Apollo 13 and after).
I looked at suits used in shows like The Six Million Dollar Man and this doesn't seem to be one of those as during the times 6MDM had Apollo style suits suits (including the Skylab ones), they were the Apollo 15 through 17 variety (and likely actual NASA training suits). Capricorn One's suits also don't seem to match either. The only other made for TV projects from the 1970s I could think of were Earth 2 (which I believe used some leftover equipment from "Marooned") and a TV movie called "Stowaway to the Moon". But I was able to find a screen cap from Stowaway and those suits don't seem to be a match for this one either.
It is not anything from a shuttle era film that I know of (so that leaves out Moonraker, Lifeforce and probably E.T.). The shuttle era EMUs are rather different. The only one I can think of that "might" have Apollo style suits would be the 1981 film "Starflight One, the Plane that Couldn't Land" as I seem to recall the suits used in that TV film might have been more Apollo based than Shuttle.
Now one thing I did notice about this suit that makes it look unique to most of the others is the NASA patch is on the left breast region. Typical practice seems to have it on the right breast with a mission patch on the left breast. Talk about an oddball looking piece, this certainly is one (and I wish I was around when the original thread was new).
