I've also heard that custom king is the place to go here, but for a few other options there is advanced acrylics who's work is excellent and if I'm not mistaken rt 4 aquarium in jersey also does custom work.
I tried the DIY with 2 20 gallon aquariums. The thing is I need a hole in one side for an outlet and both times after having the glass shop drill the holes the pane cracked. Ended up spending $200 and still don't have a sump
jeff ( custom king) made my sump and im very happy with it
that being said, if cant afford a new one built custom for you and dont have unique design in mind you can probly find a nice one in the market place here