I've printed them myself with this shrinky paper http://www.shrink-plastic.com/ink-j.....hite-250-bulk/
300 dpi and around 2.5 inches
it's good to seal them with mod podge after they've shrunk. aand you have to cut them out before shrinking them. we used a hole punch to cut the hole for the strap

I've also ordered some, but don't remember the site
but i've heard good things about these guy http://acornpress.tumblr.com/