Well, technically, most of the modern ones are replica (even if they’re a cutter). The genuine ones — hand made in traditional fashion — are very expensive. If you’re lucky, you can occasionally find gunto or other Japanese military swords from WWII in genuine antique shops. They tend to get picked up with bulk estate buys, and many of the shop owners are clueless when it comes to swords (“Furniture’s where the real money is!”). If you just want a sword with the general cutting properties of a katana or tachi, then you might order one from a forge. My choice would be something like a 9260 Spring Steel blade from Cheness, Inc (http://www.chenessinc.com/) though many others use high grade steel.