These leather collars from LXB have a locking buckle and they even included a sturdy lock! They have a large O-ring on the front that can be attached to a leash or anything you want to clip it to.

Sizes
Small: 11.5" to 14.5" (29.21 to 36.83 cm)
Medium: 14.5" to 17.5' (36.83 to 44.5 cm)
Weight: 94-112 g

Hardware: Welded Nickle Plated
Made in Ottawa, Ontario

These can be ordered in cherry red and bright red as well. Email koko@travelingtickletrunk.com to have them order one in for you!