Didier - I hope you find someone other than Hocon. They're a bit of a racket. They will not fill your own CO2 canister, you have to use one of theirs. And they won't rent you one. You have to buy one.
So for $100 or more, you get a beat up canister full of CO2. When it runs out, you bring it back and swap it for one of their full canisters for a nominal charge $25-$40 as I recall.
The important thing is to buy a size that they commonly have in stock. If you get an odd size (as I have to go in a small stand) and if they don't have any when you need gas, then you either have to get a different size. A bigger one will incur a size upgrade fee. And a smaller - when you bring that back - will incur a size upgrade fee when you trade that in for your regular size. And no, they do not issue a credit when you take a smaller tank than the one you are returning.
That's why I'd love to hear about anther place. These guys are a rip off. But I know of no other alternative.
Also... because of that size problem (not having the size you want it, when you want it) I keep small cylinder around all the time. So when my main runs out, I can swap the small one in and take my time about going to Hocon. And if they don't have the size I need, I've still got a few weeks to wait.
Subscribed... and hoping to learn of an alternative CO2 source convenient to Fairfield County.