Not to be a super creep but the Star Trek live auction pieces are up and can confirm that Captain Kirk (Pine) wears a size medium top 32 inch waist pants and size 11 shoes. Mr. Spock (Quinto) wears size large, 34 inch waist pants, and size 11 shoes. Doctor McCoy (Urban) wears size large, with 33 inch waist pants, shoe size not specified.
Honestly I encourage you to peruse the items for yourselves because there’s a lot of fun facts. For example on Captain Kirk’s Kronos costume the wardrobe department notes that Pine removed a costume piece because he got too hot during the fight scene.