marking your own isn't that hard. just make sure you have the right tools and the right glues and stuff. GL hope it turns out how you want, if you decide to go the DIY route.
It looks like you have a good design in mind but you need to think about what exactly you are going to keep in the sump. With this in mind you might want to consider splitting the line from the tank so most goes in the side with the skimmer and some goes into the sump. This way you are also...