NightHawk, did you inquire with Keng's? For the life of me I can't remember the woman who runs the place's name but I've dealt with her on the phone and she's quite knowledgeable in the field of Polytechs and Chinese AK's in general.
Those were the folks responsible for the Polytech imports in the first place, they might not be able to produce the optic (or whatever went with the odd attachment) but they should be able to provide some info, maybe even a pic.
They're pretty quick to respond to e-mail inquires, a phone call might even be worthwhile.
Let us know if you find anything out, I've had an interest in the NM Poly's for some time. I've seen some on the 'net that appear to have factory bipods similar to the Norinco (pre-ban, pre-NHM) RPK's while most don't have them. Another thing I've noticed is most have a longer buttstock while some have the standard length unit.
Good luck!
EDIT: I believe her name is Chloe...