I have searched the internet for a keyless remote transmitter for a 2001 honda...
 

...odyssey.? All companies asked whether the system was factory or dealer installed. How do I tell as I bought it new and it could be either one.

Go to the dealership. These things are generally factory installed and the new transmitter has to be programmed to that vehicle. They keep records and can look at the VIN number and get yo the right one.

If you bought the car new from the dealer and the gave you one it was factory installed. Unless you had it put on at the dealer. You need to go to a dealer and have them make you a transmitter. We had a Nissan Pathfinder that we had at least 5 or 6 made. Thats they best way to go.

Autozon auto parts stores can order them, (U.S.) Be sure to have the old transmitter with you when you order.