Longer axles? Well, there are these:
http://www.impaktrc.com/product_info...roducts_id=657
Longer axles per-say dont exist, but there are a variety of extensions, and diffeent style 17mmhub adaptors. Some just slide on like normal 14mm hexes do, where as others bolt onto the axles, making themn much more sturdy and less prone to wobble/slop.