Try this one
https://forums.alliedmods.net/showthread.php?p=880326
Here are some custom models paths:
TT
Anarchist models/player/tm_anarchist_variantd.mdl
Pirate models/player/tm_pirate_variantc.mdl
Professional models/player/tm_professional_var2.mdl
Separatist models/player/tm_separatist_variantd.mdl
Balkan models/player/tm_balkan_variantc.mdl
Leet models/player/tm_leet_variantb.mdl
Phoenix models/player/tm_phoenix_variantc.mdl
CT
GIGN models/player/ctm_gign_variantc.mdl
GSG-9 models/player/ctm_gsg9_variantc.mdl
ST-6 models/player/ctm_st6_varianta.mdl
FBI models/player/ctm_fbi_varianta.mdl
IDF models/player/ctm_idf_variantb.mdl
SAS models/player/ctm_sas_variantb.mdl
SWAT models/player/ctm_swat.mdl
Example:
sm_ss_ctskin "models/player/ctm_sas_variantb.mdl"
sm_ss_tskin "models/player/tm_pirate_variantc.mdl"