A handy person from Henderson, NV says:
April 11, 2016
Can you get this window glide? The bottom roller matches a Alenco window roller on your site. This glide fits in a slot on the top inside edge of the window.
Dave from SWISCO responded:
April 13, 2016
We do carry sliding window glides, but I can't seem to match any of them up to the one you show in your photo. Could you send us some photos of how this is attached to your window frame? That might help us locate the right part, or at least give come up with another suggestion.