What i do in init of unit-trader:

rvg_supplies_custom = ["Scienist",
["G_Respirator_white_F", 3,"CfgMagazines", 1],
["G_Respirator_yellow_F", 3,"CfgMagazines", 1],
["G_Respirator_blue_F", 3,"CfgMagazines", 1],
["G_AirPurifyingRespirator_01_F", 250,"CfgMagazines", 10],
["G_AirPurifyingRespirator_02_black_F", 250,"CfgMagazines", 10],
["G_mas_usn_gasmask", 250,"CfgMagazines", 10],
["digi_gasmaskFilter", 200,"CfgMagazines", 40],
["B_Kitbag_Hazard", 180,"CfgMagazines", 5],
["ACE_Humanitarian_Ration", 15, "CfgMagazines", 3],
["ACE_bloodIV_250", 350,"CfgMagazines", 3],
["ACE_quikclot", 40,"CfgMagazines", 20],
["FirstAidKit",30,"CfgMagazines", 10]];
this setVariable ["istrader", "rvg_supplies_custom", true];