From what i know, you will have to build or buy a HOB overflow. You can either put the refugium above or below the tank. The problem with below is you can risk flooding by over syphoning. Say you build your refugium in a 10g tank. You will have to leave several inches empty so when you turn your pumps off or a power outage occurs, it will completely syphon out and fill the refugium. Another problem with below the tank is that the return pump slices and dices the pods and whatever else you are harvesting in the refugium.
All that being said, you could hang it above your tank as a display on the wall. This way all pods and other stuff just takes a ride down the syphoning tube instead of going through a pump. Either way without a predrilled hole at the bottom, you will have to manually start the syphon every time you turn the pumps off. Unless you buy an overflow kit with automatic syphon. You can maybe build one. It consist of adding a little pump to start the syphon every time you restart the pumps.
I just realized the size of your tank and how big your fish are. You will probably need a big refugium to make a dent on your bioload and even then, i don't think you will get away from water changes. Have you ever considered using chem pure carbon. Using ion beads mixed with carbon makes the water last long and also crystal clear. I use in both my tanks.