I have a custom made hang on back refugium. I got it for 50 bucks from a local shop. Much cheaper than online ones.
I have it standing on some buckets i stacked behind the tank actually, not actually hanging on the tank. I felt better about standing it on the buckets. I am very happy with it, i have had no problems with it leaking, and i used a
1.5" bulkhead for the return line, whish is really big, but it makes very little noise. Actually less noise than my skimmer, so you cant even hear it.
I was going to use a powerhead to feed water into the refugium. but decided to used my skimmed to feed water into it, that way all of the creatures and macre algea would be getting cleaner water.
so i am very happy with mine. I would recommed shopping around at some local shops, you may find someone who will build it for much cheaper than a store would sell one. I got mine for about what the materials would cost