You think we have not already looked into those folding guns?

Check the dates on those original articles.

You can get the airsoft version from China, which has several of the parts you will need, but purposefully is not compatible with original Glock stuff, except that you can make adjustments in design to make the rest of the parts domestically, and cost effectively, provided you have around $100K up front to invest in molds and tooling. For safety and equipment stress purposes, then you go with something less powerful than 9mm which leaves us that weapon in .380 or 9mm makarov, and functionally, no better than a subcompact MAC which can also be designed to work as a folding gun, AKA the ARES folding gun from the 1980s, or the KZIN or KEDR

http://en.wikipedia.org/wiki/ARES_FMG

This weapon is more within the realm of possibility. It is not readily disguised as anything else, but then not incredibly difficult to hide/smuggle either. Blueprints have been circulating on the web.

So two workable options exist:

Resurrect the ARES design, which is likely not incredibly difficult to product in clandestine workshops, or come up with a parts kit in .380 or 9mm Makarov that works with the Airsoft FMG housing.

Consider a $50K investment gives you limited production capability, say 20 guns per month using covert sourcing of parts on contract, and then some parts made clandestinely in house, and of course clandestine final assembly and testing. In a pinch, you could likely ramp up production to 40-50 guns per month.

Sale price would initially be $2500 each, but market saturation and distribution issues would likely mean the producer gets around $1000 per gun with three to six spare magazines. Assume a worldwide market if you can get smuggling channels set up, prices remaining high with the mandatory purchase of high end accessories in a package deal to keep the weapons out of the street hoodlum crowd league.