Since drafting this Ontario police have arrested and charged multiple individuals involved in the manufacture and distribution of handguns assembled in an identical manor, likely being the source of the examples below.
A firearm seized from a male suspect on 28th August in the city of Mississauga, Ontario CA appears at first glance to be conventional though is in fact illicitly manufactured from a combination of non-firearm parts. The body of the weapon including the frame (receiver) and trigger mechanism is that of a common gas powered replica Colt 1911 6mm airsoft / .177 BB pistol which is manufactured in Taiwan. The ‘F’ within a pentagon mark present on the frame indicates a muzzle energy not exceeding 7.5 J (5.5 ft⋅lbf) usually added in accordance with German law. This appears to have been combined with a conventional .22lr slide which is branded with a Blue Line Solutions logo and made in Germany, likely by GSG (German Sports Guns). All parts required in this case are available as conversions kits from the likes of GSG and others which usually include the slide, barrel and magazine, ready to drop onto an unmodified full-bore 1911 pistol frame assembly to allow the use of smaller .22lr cartridges. In this case very little modification is required to the airsoft frame to allow the .22lr conversion parts to function, the results having been documented by in videos and forum posts the past.
A number of identical conversions have been recently seized by Toronto Police:
Two zip guns seized by police which are assembled from readily available pipe fittings. Both consist of a threaded copper pipe with a brass hose nipple for a barrel. A striker attached to a spring and a length of wire rope is pulled back and released to fire.