I uploaded a picture of a CR Laurence screen track.
CR Laurence are probably the largest supplier of window parts in the USA. I believe they have a distribution center in Wisconsin.
They dont sell to the public, but if you call them at 1-800-421-6144, they should be able to find you a glass shop in Wisconsin that stocks their parts.
Sometimes you can also find small aluminum channels in the metals section at Home Depot or Loews and other hardware stores.
Metals Supermarket, which specializes in selling small orders can sell you aluminum channels too. They have stores in Green Bay and Little Chute Wisconsin.
