You can easily make your own. Just look it up on Google. There is an article on here, but you'll need a membership.
Find some pants/pajamas that fit you and you can use that as a template. There are lots of instructions online on how to do that (it's how I made my insulated pants and wind pants).
Like this:
http://diyfashion.about.com/od/diypants/ss/How-to_Pants_2.htm
Just make sure to size up the pattern a bit to account for seam allowances and whatnot and make what will become the top of the back/butt of the pants a few inches taller otherwise you'll get major plumbers crack.
I made some with 1.6oz ripstop and rain pants with silnylon, I'm a size 32×29, and they came out to 2.5oz each (with elastic waist band).