I use a Devilbiss 525 oxygen concentrator and a BBQ propane tank for my torch. It worked well for a number of years, but has gotten a bit unreliable lately. I suspect the years of working in a dirty workshop environment have not been kind to it. I don't use it very often, since I switched to TIG welding, so I haven't put any time into troubleshooting it.
The setup is pretty simple, as you only need a regulator designed for propane and a check valve on the propane side. The O2 concentrator doesn't need a regulator or check valve. I just run mine at the max output and regulate it at the torch. The O2 concentrator has a nipple on the outlet that you can remove and the torch hose screws right on to the fitting.