fyi check out the selection on airsoldier.com. have blue has some really really small ones out there, although the smallest are solenoids Clippard SMAV-3 Subminiature Valve Fabco MSV-1 3-way Valve Fabco MSV-2 3-way Valve
The last one there I have had so much luck with in terms of pneumag and auto-sheridan/pseudo-stroker/typhoon type builds.
and for solenoids see: SMC SY123A-SG-PM3 SMC SY113A-SG-PM3 SMC S070C-SDG-32
again out of those three (and other more traditional size models) I've had a lot of success, especially in electro-cocker setups, with the last model there