The Freya magwell From Raven Concealment Systems has been very popular. RCS currently has a limited number without commercial markings for the Glock 17 (and other full size frame) Gen 4.
In addition to the flat factory GLOCK baseplates, the design is compatible with factory GLOCK +2 baseplates and copies, 10-8 Performance baseplates, Arredondo +2 and +5 extensions, Magpul Speedplates, as well as Dawson Precision’s extended tool-less magazine extensions and Ez-Off baseplates.
rcsgear.com/freya-glock-17-gen-4-sterile