At the University of Liverpool we are developing free electron masers <100 kV as a power source for industrial microwave applications. In order to be considered practical, such a device needs to have a cost comparable with conventional sources of microwave power. To achieve this we required an undulator magnet design which was considerably less expensive than the designs normally used in research-based free electron lasers and free electron masers. This paper describes techniques used to successfully construct low cost undulator magnets.