I have a thread here in this section. Look for DIY pullouts and pouches. The first post lists a bunch of places to get material. I have used DIY Gear Supply and another one listed but I can't remember of hand since I am currently mobile.
I made 8 pullouts so far and two meat baggies with about 55 dollars spent in materials including the shipping cost, i've got enough materials left to make probably two more meat baggies and 4 or 5 more pull outs of various sizes. If you already have the sewing machine then its definitely worth it.
To me, is also great because you can make stuff to a certain size to fit what you need. You could also size them to maximize limited space like on the wings of a Nomad or the lid off some pack.