When I find myself similarly stumped, I tell myself, "A solution is at hand within 15 feet of where you're standing right now."
Example: a mountain bike front derailleur whose spring anchor point had snapped off. Jammed a twig into the derailleur to lock it over the middle chainring. Rode home, looked around, spotted a slit inner tube I'd thrown in the trash, cut a section out of the tube, rigged it to replace the spring. The derailleur shifted just as well, and maybe better. Used it that way for a couple of months until I got around to picking up a new front derailleur.