The strange thing is I don't recall seeing one, although we'd think it would be pretty obvious to have one. I guess the reason why there's no site describing sumps is that sumps are incredibly simple. It's merely a container of water with some baffles inside to help stop bubbles from entering back into the pump chamber (and ultimately back up to the tank). You can get a little fancy with your design if you have some specific plans in mind, but almost all sumps are simple containers (rubbermaid containers or small tanks). I'll dig around a bit.