The housing isn't reproduced. Your best bet is to have a replacement fabricated using the original as a pattern. On occasion, Dennis Dahle (firstrider on the ford-trucks.com 48-56 forum ) will have pieces available to sell. Dennis is the self proclaimed King of the Magic Air heaters but routinely scavenges, rehabs, and sells parts for the 48-50 versions as well.
Napaonline.com part number BK6551020 for the motor.