Try these people. http://www.dannoenterprises.com/ You'll have to try and match what you have (OEM) to what they carry. I haven't totally figured out the exact replacement strips that I need yet.
It's on my to-do list, but I've never contacted them.
I believe he also hits the Florida swapmeets like Zephyrhills, etc.
As you are probably aware of, these channels are NLA from GM.