There are 1903's(some that are considered unsafe to shoot), 1903 Mk I's, 1903A3's and for the affluent, 1903A4's. (I've seen one '03A3 in decent condition in 40 years. Haven't looked very hard though.) However, which model you want matters.
Like any other milsurp you have to hunt for 'em. There's no such thing as a distributor a retailer can order 'em from these days.