Where can I find guidance on uniform items for horse-mounted teams and caisson teams for honor guard?

First, ss their specific pants for riding horses similar to Army Service Uniform (ASU) that you order, or do you modify your pants for riding horses (e.g., breeches; i.e., this used to occur during the Civil War period). Tall English riding boots are often used to ride for horse-mounted patrols and caisson teams. Which brand of boots is used for horse-mounted military teams? Or, is it the officers responsibility just to buy their own and get ones that look standardized? How does a caisson or horse-mounted team go about getting these specific uniform items? Thank You Much