Protect transfers in a bag?

I canvas-like material that says it is ideal for use with the transfers. I would use this to make my own fabric for a bag. How can I protect the finished product once I have the bag sewn together? I was thinking of trying a flexible varnish, but any other suggestions would be wonderful.

You could try this product: http://www.pearlpaint.com/shop parentID ~ 8672 ~ ~ CategoryID 8667.htm

Cutting Fabric Transfer on your Klic-N-Kut