Here is a link to a PDF file on the
Gemini Surf Rescue which is built to SOLAS specs.
Pictures below are of a unique American designed fully inflatable rescue boat by
Zumro. Ugly as sin, but if you want bouyancy, more bouyancy, and still a little more bouyancy, this is the one.
Edit; I should have asked if you were specifically looking for RIBs vs SIBs, or if it mattered. Google searches of 'SOLAS rescue RIB' or 'SOLAS rescue inflatable' turn up a few more manufacturers.