I wear a cowboy hat with my kilts quite often - I've found that pull on boots do not look good with a kilt, but lace ups do just fine. Wide belts with a nice silver buckle complement my black denim UK nicely.

My daily attire is a business casual polo, UK Mocker, horse hair belt with sterling silver buckle set and brown lace up steel toe Ariat boots. (I only don the AHC on the weekends)

Yes, you can find a denim kilt, and no, UK is not the only ones making them.