I added these to weapons.txt and it seems to work. When viewing current saved loadout though, it shows up as "NVGs: Yes" probably because it was never intended to handle armor.
Code:
"Kevlar Vest"
{
// General
"weaponentity" "item_kevlar"
"weapontype" "All, Equipment"
"weaponslot" "5"
// Restrict (core)
"restrictdefault" "no"
"toggleable" "yes"
// ZMarket (module)
"zmarketprice" "650"
}
"Kevlar Vest + Helmet"
{
// General
"weaponentity" "item_assaultsuit"
"weapontype" "All, Equipment"
"weaponslot" "5"
// Restrict (core)
"restrictdefault" "no"
"toggleable" "yes"
// ZMarket (module)
"zmarketprice" "1000"
}