Have you ever considered a hookah setup? If I recall correctly, they provide one an atmosphere (33') of depth capability. It's something that I've wanted to do since 1971, but making a living took precedence until recently. Now, I fear I'm too old and out of shape to risk any kind of solo diving.I have SCUBA gear but getting air around here is another story. So I've always free dove usually with a 5mm suit, belt and fins. I've pulled bottles upwards of 15 feet but I'm at the point where doing that all day, I'm nervous about shallow water blackout. Also I cant stay down long enough to pick through the bottles carefully and I'm sure I miss a lot especially small inks and such. So I'm getting a Grumman Sport boat and using tanks when I start back up again.
As a retired Firefighter I can say that I did fill tanks for Divers over the years. We had two whips available for scuba cylinder fills ( Firefighter cylinders use a different style of tank valve ). I would approach your local Fire Service & talk to them about it. Anyone can purchase an air compressor, but most air systems have several large, high pressure air storage cylinders that are married together to form an air fill "cascade system" - the compressor runs till it fills these cylinders to their rated pressure, then shuts off, starting up again as needed to keep the cascade system full. All this equipment has to be purchased, plumbed together with stainless tubing, then maintained ( regular air filter & compressor lubricant changes ). That's a pretty tall & expensive order!Where I am now... I guess the fire dept. will fill tanks for divers. And I'm going to be stationed here for a few years anyway. How about rebreather or hookah. Hookah wouldn't be good too many snags like you said. Think I would need to be certified to buy and use a compressor. Rebreather would be nice if I hit the lotto.