Here is a Full Sized grip for the RP3 & RP3+, with one file for each hand so it fits on smaller printers.
Retroid Pocket 3/3+ Full Grip (Solid)
RP2+ with 3d printed grip : r/retroid
BeefyGrip RP3 – Beefy Retro Gaming
Retroid Pocket 2 Review - HubPages
3D Printed RP2(+) Case/Grip : r/retroid
▷ retroid pocket 3d models 【 STLFinder 】
Retroid Pocket 3 Grip by MakeItHappen72 - Thingiverse
Anbernic RG351MP RG350P and RG350M Grip Case 3D Print STL File 3D model 3D printable
Retroid Pocket 3/3+ Plastic Shell
Portable Frosted Silicone Protective Cover for RP2+ 2.5, Dockable Case Compatible with retroid pocket 2s, protective cover case compatible with RP2 Plus, Soft and comfortable to the touch, compact fit
3D-Printed Grips for RG350 and RG351 Devices – Retro Game Corps