You have to get the RABC via US Mail with the appropriate documentation, the Canadian License and Sportsman Card can be purchased over the phone. Both take a credit card and some lead time.
Mine usually arrive in about three weeks. But I order in March.
you can apply online at Rainy Lake Sports and they will mail it to you. You can always head under the bridge at Rainer and go buy one at the same place. Saves the HASSLE of crossing the bridge and going through customs