That's the one, not a seller I've used.. for the RF-602 I can recommend either Trevor at
CotswoldPhoto or using
HKYongnuo. If you get the right connector cable as well (C3 for the 20D?) you can use the trigger as either a wireless flash trigger or as a wireless camera shutter trigger (to do both you'd need another transmitter/receiver pair).
The RF-602 seems to have been superceded by the RF-603, looks like a useful replacement as it standardises to a single transceiver and only one battery type. Worth considering, not used the RF-603 myself.