Numrich used to carry tons of the A1 take off stocks, both the trap door storage and the solid foam filled types.
According to the online catalog, they only have two of the trap door models (and they look pretty ratty):
https://www.gunpartscorp.com/products/564730A
Same for the foam types. Those used to be $6, now they run for $25
The good news is these stocks can be cleaned up. I also believe the trapdoor A1 stocks (original ones) are more substantial than the modern A2 types from Colt and other manufacturers. Plastic is thicker and they weigh more, despite being 5/8" shorter.