A one-stop shop would quite easily have warehouse stock of demos to sell cheap or in bulk, bought any time after the record was released.
A note on the pressing details of this record. Warner Brothers at the time had their releases largely pressed at Columbia factories. The various numbers quoted here, from 1A up to 1E refer to different lacquers. When the record was mastered a number of lacquers were cut and sent to the various plants. Each plant would have received a different lacquer with a unique code, so the A and B numbers do not refer to whether the respective side was the plug side or the flip, just to which plant it was to be pressed at. If a lacquer had to be replaced (either for a fault or for stamper wear) it would then become 2A, [or 2B etc.] then 3A etc.
The typesetting for this release was done at Columbia Santa Monica in California, which did the typesetting for Warners Reprise and then sent artwork/films to the other plants. The Columbia plants (Pittman New Jersey, Terra Haute Indiana and Santa Monica California) pressed both styrene and vinyl and it was quite common for the promo to be on vinyl and the issue to be cheaper styrene as is the case with the Bobby Sheen record.
Columbia didn't use the brown, see through plastic which the bootlegs are supposedly made of in 1972. This material is not generally seen until the mid to late 80s, when the number of vinyl pressing plants in the US had decreased from dozens to just a handful of functioning factories and this became the default material for many vinyl 45s.
If anyone has a bootleg of this it would be really helpful if they could photograph the dead wax and post it up here. I'd be interested to see if these have the stamped matrix which a genuine Columbia-pressed record should have, or whether it's scratched in.