Not custom, but still high "bling factor.
Note that those are 1/2" barbs, rare for such a small res.
I got it at:
www.performance-pcs.com
It works great on an Eheim 1048, but an Iwaki 20RZT overwhelms it. The air goes right through! The inner chamber is only 1-1/4" (D) X 4-3/4" (H).