These are both very low cost and plenty adequate for training and backup.
Dual Electronics We have one and they work great. Also serves as external GPS for iOS devicesGarmin GLO 2. Have not used one, guaranteed to be excellent.
Garmin GA38 Just $78. Includes a long cable, but with BNC (coax) connectors at each end, so you will need to go from BNC to USB to get into the computer.
• Handheld dedicated GPS unit: It may take some research, but some of these can be wired to your computer to use as a primary source of GPS. We have many of these dating way back, but the example we use here is our Garmin GPSMAP 78s. This is an old one, it was one of three used by team MAD Dog when they set the record for the R2AK in 2016—we had the pleasure of working with them in preparation for the race. Connecting these hand held GPSs to the computer can take some research. It is usually not covered in the manuals. We explain below how to do it with this one.