If you are OK using manual flash power, then the answer is easy: get a pair of Yungnuo RF603 CIIs.
They're cheap, robust and function well.
If you want to go down the e-TTL route it's more complicated.
The simplest would be a Canon ST-E2 unit. But that uses Infrared triggering, with all its drawbacks (range, angles etc).
Otherwise you are looking at a third-party TTL trigger for Canon - and that is a bit of a cowboy market for flash units that old.
Even the product that should stand out head and shoulders above the rest (The Pocket Wizards Flex system) is frankly bloody dire.