I had my LFS
do a custom sump for me as I didn't want to mess things up if I did it myself (and they used glass sheets). All you'll need is aquarium safe silicone, a glass tank, and some polycarbonate sheets from Homedepot.com or some place. You might be able to ask them to cut it to the length you want if you don't have the tools for it. You also need a tool to make sure things are level & straight (don't know the name of this tool
). You can look up some different designs and methods of making them online, or youtube has a lot of vids about DIY sumps...heard they are pretty easy, MUCH cheaper, and you can make them any way you want!