I believe that the Metz 54 doesn't have a PC cable, and I'm looking for the cheapest option. The T2i doesn't have this built in does it?
Here's some information regarding optical slaves from Syl Arena.
What you need, though, is the simple SCA 301 standard ISO foot, which has a sync port. This costs about $12.50, and you use it in combination with this cable or similar, which is PC male to 2.5mm sub-mini.
With this approach, you'd still need an adapter with a PC sync port on the camera's hotshoe, as none of the Canon Rebel line has PC sync ports. (There goes another $12.)
I don't know what connectors the Mets 54 has, but there are some options that will work with any flash:
You can get a cable that connects to your camera's hotshoe on one side and has an hotshoe-like connector on the other side, something like this
You can get cheap radio triggers with hotshoe connectors, for example this
Both products I linked to are meant as an example, they are just the first options that came up in an eBay search, I don't own and never used any of them (but I have used similar radio triggers with my T2i and a flash with no PC sync post).