Lone Wolf Distributors, purveyors of all things Glock and Glock Related had this on display at the NRA convention:
It’s one of their Timberwolf frames (compact model) cast in clear plastic. Unfortunately they are not for sale. When I asked if they would consider a limited run of them, they told me that they have looked into it but they have not yet found a clear polymer that will bear the stress of repeated firing. They also mentioned that some parts manufacturers have shown interest in the transparent frame as a way to display internal parts and how they function.
It would certainly turn some heads if you showed up to an IDPA match with a mostly clear gun (and clear mags, too). I think a satin finish chrome or stainless slide would look perfect on top.