How can I cold smoke without any of the equipment?
There are smoke extract products available, such as Liquid Smoke and others with the type of wood smoke flavor desired being specified. With only a few hours to work with, you may wish to inject the solutin to speed up penetration into the meat. Brine or marinade diluents may be options to explore depending on your desired outcome. 

Even so, minimal " equipment " such as the injection syringe and a container with some means of covering for the leg would be helpfull, or at least a foil or other wrapping for the 
lamb to keep juice in and atmosphere out.