A special adapter from Amazon, like $20.

Be sure to refill by weight. Buy a full screw top canister and weigh it with a kitchen scale, note the weight in grams, write it on the can and in your phone.

Then later, when it’s empty, put it in the freezer for several minutes, pull it out and refill it with the other canister, but only fill it to the weight it was originally at. It will gladly take more gas, but there will be less headroom or no headroom, and the canister has a high chance of exploding.

The Internet will tell you not to do it, and how unsafe it is, how the valves aren’t meant for that many uses, and it’s definitely gonna explode etc etc. But if you do it smart, you’re fine. And don’t reuse the same screw canister many many times, you’re already saving money, reuse it a few times then recycle it and start over.

Edit: this is the one I bought, it’ll do the trick. https://a.co/d/eHJDQGL

Also NEVER EVER EVER refill them with any amount of propane! Yes the normal canisters come with a percent of propane in them to help in cold weather. But getting the partial pressure mixture right is almost impossible at home, and propane will definitely make your canister explode. It’s vapor pressure is too high. That’s why the pure butane canisters are so thin, and the green pure propane canisters are so thick and heavy, because they need to be to hold back the pressure.