Where can I find an overflow cap?

[Sixpack_Sid]

I have a 75 Duster with a big block in it. I have the original overflow tank, which fits perfectly in the engine bay, but the cap is fitting loose on the tank. I've looked online at classic industries, jegs, year one, etc and cannot find the correct cap. Mine does not have the 2 lines coming out of it-it is a closed cap. Does anyone know where I can find this cap or is there any way to "shrink" my cap to make it fit again? Thanks!

 

[Bennoel 10]

Maybe try covering the opening with a thin piece of cloth, maybe something like an old cotton handkerchief grandad used to have. Then screw on your cap and trim the excess off. Should tighten up enough until you find the correct lid.

 

[Syleng1]

A wrap or two of electrical tape should do.