Great costume choice, I have all of my Dads Blackhawk comic books from the 50s, fun series.
Just to correct Riceball's identification of the pants. They're jodhpurs, not puttees. Puttees were the leg wraps used in WW1. Jodhpurs are still used in uniforms, especially motorcycle police. Sometimes jodhpurs are known as riding breeches. This information may help you locate a supplier more easily.
The cheapest pairs of riding breeches I've seen on the net have been East German army pants, I've got a pair, they fit nice.