I’m in the process of setting up a small e-com business and have done some prototyping abroad. Portugal has some excellent small leather manufacturers and I’ve done some polo/dressage boots with a company in Pakistan. I think they turned out pretty good, but not perfect. The polo boots were definitely better. Why? Because this particular manufacturer has done many of them. So everything is about patience and repetitions.
Bridles are an easy job compared to eg a saddle or a boot, so you could just work with a decent cobbler, but if you want excellent quality you will need to shop around. My advice would be to always do a pilot with more than one because you need fallback options, that’s just how it works with outsourced product dev in general.
And expect sourcing to be a bit of a process so I wouldn’t rule out international manufacturers at all. Unless you find someone hyper-local, I wouldn’t even say that it’s faster to do it in US. American distances are so large that an express international fedex won’t necessarily be that much slower. Shipping those boots took only a week and that’s with customs and all. A bridle you can probably even ship in an envelope so much lower complexity & expense.
I’ll also add that you should do multiple iterations, when testing the producers because one of the big lessons I learnt is that it doesn’t really matter how good someone is as a baseline, but can you communicate well? Can they receive feedback? Are they quick with iterations? Those things really matter a lot more than perfection in that first order.