I've DIY'ed every one of my ballasts. Being fortunate enough to live in a town where they demolished 2 major steel plants and foundries, I had access to as many 400w and 1K ballasts, both MH and HPS, as I wanted. And I bought as many as I could get my hands on, believe me. $25 to $50 ea. with bulbs and reflectors.
They were all High Bay and exteriorsecurity lighting and had to be modified for remote ballast application, but it's no biggie. You can even adapt an HPS ballast to run a MH bulb. Not recommended, but it works.Anyone need to know and see how I do it, hit me up.
I too have tried every thing I can think of to find appropriate enclosures for the ballasts. No joy. I just re-use the original enclosures now.