Seems I've broken two buckles in just the last 6 months; I have been measuring every single shot since going to ELR comps. I was an early adopter and have plastic buckles on both of my bayonets. I carried a spare but that only lasted so long before it broke as well. The buckle is sewn on the strap so a field repair could only happen if you had a replacement strap/buckle. Or...
Metal buckles, slick clips and split rib buckles can easily be found online.

Metal buckles, slick clips and split rib buckles can easily be found online.