I found an eBay seller of the top-notch quality G-Works any-to-any adapter / converter fittings, shipping from Korea is pretty reasonable at least much cheaper than dealing with G-Works directly.
https://m.ebay.com/sch/i.html?isRefine=true&sid=lstefano2015
Note this type tank is called "canister" or "nozzle" valve.
The round squat style usually used for the little backpacking camp stoves is here called "screw type"
And for Coleman 1"-20 fittings they use "1 pound".
Yes a bit pricey but well worth it if you're going through more than a few bottles per month, propane by the gallon is so much cheaper will pay for the adapter pretty quick. And no more looking for the butane!
Plus very well engineered, should last a long time.
If you can't figure out from the pictures, forget the text
, post a description of what you're trying to do and link to the adapter you're asking about, and I'll do my best to help.
Note as you are browsing you'll start to see Schenzen knockoffs very cheap, personally with flammable gasses used inside vans or tents I'd avoid these like the plague, but if anyone tries them let us know!