Breast Collar Set

Okay so if you don't know a POA(Pony of America) is a breed that has been bred with a shetland stallion and a appaloosa/arabian mare. Throught the years they have gotten bigger, and now my 2 stand slightly shorter than a Arabian, however much taller than a shetland, and they a great horse for anyone. I mean it's a great height, but finding tack is hard. I have tack all set for my mare, but now I am starting to work with a 6 year old gelding, Reggie, as well. Georgie is very well behaved, and I don't need a tiedown or breastcollar with her. But for reggie I am looking breast collar and a tiedown. He really got off on the wrong track and I am going to attempt to "retrain" him.

So heres the thing, the horse tack is usually too big, and the pony tack is too small. Where should I get my tack? Looking for a nylon set of headstall, tiedown, tiedown strap, and breastcollar. Thanks in advance!