I believe a standard 5 gallon glass aquarium would fit that. Anything acrylic and you're probably looking at a custom job (or a Rubbermaid-style container). Depending on where the tank is located, you may not want the sides transparent at all (my tank is near my bed, so no chance for reverse photoperiod unless I were to paint the glass).
Plumbing is rather dead simple, though there are many approaches to fuge plumbing lately.. Anthony Calfo has been a strong proponent of utilizing heavy water flow (I think he said he keeps his chaeto rolling at all times and it grows like stink), whereas traditional fuge culture has opted for slower water flow. I guess it really depends on the types of algae you are going to culture.. I really found that the coolest incidental algae growing in my tank always popped up right in front of my surge output. Maybe high flow is the answer, or an extra powerhead within the fuge to keep things movin'.
Speaking of surges, here's what I did with my fuge:
I combined it with a Borneman surge so that the top 4.5 gallons or so actually surge back into the tank. That's an early shot.. Since then I've cleaned it up some. Pod populations are soaring, the halymenia you see there went through a bit of a dieoff (all I keep hearing is you can't transfer it very well) and is showing new growth, and the chunks of LR in there are sporting new stuff too.
(And on the business end of the surge in the display I just had some cool turtleweed, mermaid cups, and scroll algaes start coming up)
If you just want to plumb it simply, you really just need a bulkhead coming in and out, and just mentally treat the fuge like your display and the display like a sump would be.. Same principle, only you want to limit the ugly equipment on the bottom side.