All of those issues can be solved by sitting it on top of your amp.
Kinda stops it being a pedal though...
I had a VT1 EQ for (Many happy) years and used the 12v supply from my Donner DP2 power unit - delivers 12v at 500mA, so I just used a polarity reverser that it came with and never gave it a second thought.
Before using the Donner I used to use a 12v laptop power supply with no ill effects - 12vdc at a couple of amps and it was already centre positive, so no need to invert the power supply.
The only thing that I've heard that came even close to the DHA unit was a BlueTube 903 Tube drive. 3 band EQ and a 12AX7 (ECC83 to you and me) tube that is fully enclosed.
They tend to be rare and expensive these days though.
TC electronic do a Tube Driver for a LOT less than you'll find DHA kit for, but I've never used one.
As with anything there's the Behringer version - the VT999 which again uses an honest-to-goodness vacuum tube with an EQ circuit, but again, I've only seen them.