A while back, there was a huge sale on Lowepro Nova Sport 35L AW bags. I jumped on it and was quite happy with the bag, except that it was very floppy. The floppiness has been fixed with a stiffening frame. Below are a few photos, all that's needed is a small welder (a 110V flux core welder would do), some rod (I used 1/4" and found it to be perfect size/strength), and a grinder to clean it up/round off the corners so it doesn't penetrate the bag. It works very well, the bag sits very well (even if it's loaded unevenly) and I couldn't be happier with it now.
IMG_0102 by Tyler Gerritsen, on FlickrI thought it would require gussets to prevent the vertical posts from folding over, but after using it as-is for several months I've found it to be just fine without.
IMG_0103 by Tyler Gerritsen, on Flickr
IMG_0104 by Tyler Gerritsen, on Flickr
IMG_0105 by Tyler Gerritsen, on FlickrI made a few attempts to get the right fit... Snug but doesn't stretch the bag.
IMG_0106 by Tyler Gerritsen, on FlickrThe frame is hidden when the internal pocket is inside the bag.
IMG_0107 by Tyler Gerritsen, on Flickr
If serious, PM me.
