Magnifying glass that follows cursor for canvas

I'm working on a t-shirt designer for a client of mine and I made it using html5 canvas. The shirt designer is now finished but he requested I add a magnifying glass (something like this: http://mlens.musings.it/). I've found a lot of similar scripts out there, however, they all seem to have one thing in common they use a small and a large image. Using canvas, however, I have a different scenario and have been stumped on how I can add a magnifying glass to magnify where ever the cursor is on canvas.

Are there any scripts that exist that can get this done? or what other options would I have?

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