I've made few halters for my Schleich scale model horses.
Used: leather, metal wire, some necklace chain, glue. Buckles and hooks are ofc all working and I cutted the leather straps only with my scissors. Tools used: Two thin-nosed pliers, round pliers, cutting pliers, two TINY (tiniest I have seen...) clothespins, barbecue stick. I think that good width for a LB scale halter strap is 1 or 2 mm. And yeah, I cut all with scissors and sometimes a bit with a scalpel.
This halter is too small for that horsie, but it's still better than too long or large halter what I generally do as too easy, especially in this scale.