The dive shop I use for my fills use these din-to-yoke fill adapters. They fill my tanks to 3,800-4,000 every fill. They’ve never had an issue. I get 4-6 HP tanks filled a month. In excess of 100 HP fills over the last 2+ years. Their fill adapters have never had any issues.
You Sir need a compressor...at least down there it's ~ $3.xx for a fill? Up here it's $12 / tank!