Cap for toilet valve
 

I just purchased a 1971 Hi Lo and I love it. However, the previous owner did not replace the cap on the toilet valve so it runs water all over the floor. I have looked around and have not found one that will fit. Any ideas as to what size and what kinds of threads the cap needs to be? Here is a picture of the valve and the place where the cap needs to be. Any thoughts would be appreciated.

Try a wholesale plumbing supply house (not a hardware store like home depot) remove the valve a take it with you,that's the first thing I would do. It might take a couple of different adapters to make it work. Option 2, try to find the manufacturer of the toilet and google search the make and see if they have parts available, you might have to buy a complete valve just to get that cap.

OR!!!!
right behind the valve that is leaking there is a shut off for the toilet line. It is 1/4 turn.
The cap that is missing is not the only part in the cap. there is also a spring and ? also.
The leaking flush valve is available from Amazon... sea/land in the name

that way the toilet will work

This may be the one. A fellow member shared this with me a few weeks ago.

SeaLand SE314349 Water Valve Kit:Amazon:Automotive

Solution!
 

Thanks for the tips. I ended up cutting a circle from a sour cream container lid and putting that in the fitting. It has held just fine. Now my problem is the holding tank under it. It has several cracks. Does anyone know if the original 1970 tank is ABS or Polyethylene?

cracked black tank.
 

I'm not an expert. What about dropping your tank and use some leak seal stuff made by Rust Oleum? Should be cheaper then as seen on TV Flex seal. I got my can at Walmart.