Tsunami on King East (at Ferguson/King) has been selling them for years and probably knows their stuff the best. I believe there's also Silent Rider on James North though I don't know them at all.
This was a 2008 article in the Spec I read when it first came out:
http://thespec.com/article/402337
I don't know where you get these ones, I was looking at it a couple years ago. but there's e-bikes that come with detachable li-ion charge packs so you can park the bike in a basement/lock it up and charge the battery pack inside - that's a good option to have.
This is a long way away, but someone I know knows these guys and vouches for them -- and I trust his opinion
http://www.sarniaebikes.com/