You can use this, release it, whatever. You can also code your own. Cooked this up in about 5 minutes.
amx_addresmodel models/bla.mdl
replace models/bla.mdl with the model you want restricted.
It writes to file addons/amxmodx/configs/restrictedmodels.ini (You can also do it manually)
It disconnects the player then prints in his console that it's restricted. I believe you can use the fakemeta module to supercede him changing his model or something. I havn't tested it, so best of luck.
(Needs Engine, and fakemeta to run properly.. If it was CS-only i wouldn't need engine, just cstrike, but it's multi-mod)
If you use it, and it doesn't work, just tell me man.