I have three 4-bay Proboxes and reading the feedback here, I believe that the PSUs are inherently of low quality. I had one Probox (bought from Australia) die early, seems the board itself was faulty. Then I got two Proboxes locally, bought from Dynaquest, which left me with one extra PSU. The PSU of one of the locally-bought Proboxes early on had issues, it would only work intermittently. I didn't have it replaced under warranty though because I thought it was a hassle and I had the extra PSU from the dead Probox anyway. Eventually this PSU died, leaving me with only one working PSU.
The good thing about the Probox PSU is that it only requires one voltage (+12V), unlike some enclosures that need +12 and +5V. Moreover, the pin layout of the PSU's 4-pin plug is clearly marked in the PSU's sticker, i.e. which pins are +12V and which are the ground. Knowing this, I built a so-called "PSU tap" i.e. I tapped the 12V rail of my computer's PSU to power one Probox. The current requirement of the Probox is just 5A, which can obviously be supplied by a computer's PSU:
This is a simple DIY project that only required components salvaged from old PC parts (e.g. expansion card bracket, male and female "Molex" connectors, LEDs), a small piece of leftover breadboard and some soldering equipment/skills. It powers the Probox perfectly, and even if the last PSU dies, I'll just connect the salvaged 4-pin plug to the "externalized" Molex connector and have the computer's PSU power my two Proboxes:
If you really can't find a specific replacement PSU, the foolproof way to power your Probox is to use a computer PSU. That's because 12V is a standard PC PSU voltage (along with +5V), and 12V rails typically have a lot of amps so that one PSU can power a bunch of Proboxes. It's not necessarily a PSU powering an actual rig, since you might be using the Probox for an NMT or something. Rather, you can just hunt for a working PSU from obsolete or junk computers so you won't have to spend anything. You need to DIY it a little though to put a power on switch and maybe a load resistor for some PSUs, but it's a surefire way to power a Probox and it's nearly cost-free as long as you can look for an obsolete computer with a working PSU.