Marty,
Sorry for my late reply, I have been in the middle of a interstate move.
As Radagast said Survival Arms is your best bet, otherwise I cannot say where you can get them. In thier original form, the collapsable stocks are an illegal inport. However in California you get look a like stocks that cannot adjust, to comply with the laws there that are very similar to those in Australia.
Also in Sth OZ, quite a few early model 7615p came in with the collapsable stocks OEM. Customs of course has put a stop to that!