The William Optics Slide-Base with 50mm clamping guide rings will improve the overall rigidity of your small guidescope setup. It employs a Vixen style dovetail mount, which will attach to a variety of Vixen style mounting bases by numerous vendors.
The ring inside diameter is 54.8mm, with a non-marring material that reduces this diameter to that appropriate for many 50mm guidescope tubes. Due to the reasonably large field of view delivered by such short focal length guidescopes, it's not at all necessary to incorporate any adjustment in aiming. And so the rigidity offered by the uniform clamping action of these rings lessens the chance of differential flexure.
The dovetail is 100mm (4") long, and the assembly weighs 185g (6.5 oz.)