Nearly all competitive events will require you to have a transponder. This information is usually detailed in each events respective Supplementary Regulations.
Sometimes the event organiser or promoter will have the facilities to allow the rider to ‘rent’ a transponder for a specif event. To check availability the rider should make contact with the club or event promoter to see if this service is available.
Alternatively you can choose to purchase one. You will find all the information to make an informed purchase decision HERE.