Pitsco has a good starter kit for solar cars that includes Solar panels, motors, multiple gears sizes, axels, wheels, 3V battery holders and accessories for 15 or 30 students. Here is the link: https://www.pitsco.com/Solar-Vehicles-Getting-Started-Package
If you already have a set of solar panels, this is a more budget-friendly bundle: https://www.pitsco.com/Competitions,-Clubs,-and-Programs/Junior-Solar-Sp...
With either of these kits, you will need to buy the motor mounts separately. This is an option: https://www.pitsco.com/Syringe-Motor-Mounting-Clips
Let me know if this is what you are looking for or if you need more help.