See if you have a supply place near you for fire equipment. Back in 2015 when I got my 3 used scba 45 minute tanks from a fireman, one was still on current inspection(barely), one had a end of life coming up shortly and was out of cert by a few weeks, and one was just a couple weeks out of end of life. I paid less than 50 for all 3, he threw in the out of date one for free and took me to the fire station and filled the one still in cert, he wouldn't fill the other 2 as it could mean his job if it ever got out. Checking around, I found a commercial fire supply place that did hydro not 10 miles from me and took them there, the fireman I bought them from suggested looking for one instead of a scuba place. The two that had not reached end of life cost 25 dollars for both, not each, to get a new 5 year certificate, where all the scuba places wanted much more than that for each. Don't know if that is normal, or just the one place I happened to have near me. Worth checking out. Talking to the person that did the hydro's, he asked what I was doing with them and if I had the end of life one with me, and i did. Told him about using it for PCP's and he said to bring the end of life one in and leave it. Being past service life, it cannot be recertified, but he hydro'd it without certifying it and told me it was fine when I picked them up a week later, didn't charge me for that. I have no idea on fill prices, I have a compressor.
BTW, he was probably being extra nice to me since we talked for over an hour about our firearm collections, and made plans to get together to check out a couple of each other's special ones.