Hi Ken
As far as I have read through researching your question, you can go to the hardware store and purchase am end cap that fits, use gasfitter tape (like a teflon plumbing tape) seal the end.
Testing
Before using a
propane appliance, particularly if you have just connected a cylinder to it, check for
leaks using the following method:
1. Make up a dish soap and water solution.
2. Turn the cylinder valve on with the appliance shut off.
3. Spread the soap and water solution over the hose and the connections with a paintbrush.
4. Any
leaks will result in bubbles forming in the solution.
5. If a leak is indicated, shut off the cylinder valve.
6. Don't smoke while checking for
leaks
Here is a picture I found in my travels
http://www.propane.tx.gov/safety/safeuncapped.html
HTH
Graeme