Low cost hyperbaric test chamber?

Hi, has anyone here built a hyperbaric test chamber for your ROVs? I’ve made one from a water filter housing for 30€, but it only goes up to 10 bar, and can only fit small parts. I’m looking for a way to build one capable of 50 bar, with space inside 150x400mm or more, as cheap as possible while still being safe (meaning, able to degas properly). I’ve considered second hand hydraulic cylinders, pipe spools with blind flanges, threaded pipe nipples with screw-on end caps, but at these sizes all of them are super expensive (200-300€ at least). Any advice?

EDIT: one more thing, if use this test chamber to test parts to implosion (such as electronics enclosures), I realized the implosion would cause sudden spike in pressure, local cavitation and shock waves that might blow the chamber apart. Are there any practical ways to prevent said damage? One idea I have is to fill the electronics enclosure with water, but leave some air inside (like, 95% water, 5% air) to still make it implode, but have less air to create smaller pressure shock. I also read somewhere that such test chambers are often filled with plastic spheres alongside the tested part, and they somehow absorb the shockwaves - although I don’t really get how that works, and what characteristics these spheres must have (solid? hollow?) to make them work. Any insights would be appreciated.

I’ve looked into this too. I’m building a small glider, and received a grant (~$8k CAD) to build my test chamber. I built mine from pressure rated pipe flanges from McMaster Carr, though I’ve seen other people using large hydraulic cylinders, they are cheaper but time consuming to take apart and put back together. Everything in mine is rated for 600 PSI (41 bar), but for a safety factor, I set the blow off valve to 500 PSI, (34 bar / 350m). I crush all kinds of stuff in there, and have never had a problem with pressure spikes.

I’ve done a lot of looking myself for cheaper options, but I needed the 7.5” ID, and there really wasn’t anything else. there are sites that sell pre made pressure chambers for industrial testing, but they are small and start at 20k USD. I’m sure you could get this made cheaper, but since i had the grant money I used a certified welder, and had the welds tested at a third party inspection company. it also weighs 400 lbs and is a pain to move. But let us know if you find another way!