Screen corner keys

Per attached photo, I'm looking for replacement keys for screens provided by Sierra Pacific Windows. The keys seem normal 3/4" but the tubing used for the frames has a profile that may be unusual. I've attempted to draw the interior sizing. Tube is 3/8" x 1/2" with a flange or tab width of 9/16" Let me know if you need other measurements. The keys lave a logo "TF" and numbers such as 29 and 16.

Thanks,
Al