I'm assuming you don't think that a Pronto is "fairly cheap" and you are looking for another type of remote control :)
The cheapest and most effective is an RF remote control and RF transceiver. This type of remote does not require line of sight control and has a very good range.
If you look on our web site at: [Link: ourworld.compuserve.com]
you will see a list of clearance items. You can pick up an RF remote and Transceiver for $21.