Short answer:
You can't. Not in airsoft form. Not one for the TM AK-47S, anyway.
Long answer:
1) You can try and get a receiver from
Trapper Industries. It's expensive though, doesn't quite look right, but it does fold. You'll need to get a retailer to import it for you probably, since metal receivers and customs don't agree with each other.
2) Buy the real steel stock and follow the tutorial
here.
It'll be cheaper, look better, but won't fold.