I will start by saying do this at your own risk! you will be modifying a propane torch head.
I started with this $12
if you don't know it has right hand threads and an o2 tank has left hand threads.
I took it apart leaving only the main body that screws on the the o2 tank.
then i took a carbide scraper (though you could use a dremel tool or sand paper) and took the threads of the torch head down to about half of there original height.
now putting the torch head in a vice you can (cross)thread an EMPTY! o2 tank in to the brass torch head by pushing the tank hard as you turn it. (the torch head being made of brass is softer then the steel used in the o2 tank.)
once the left hand threads have been created you can reassemble the torch head and put on a full tank to test it.
this took me about 15 min and i have a functioning o2 valve.
Again i will repeat this. DO IT AT YOUR OWN RISK!