well thats good to hear. Ive found these frogs will eat only if they are hungry (which is generally most of the time!) but if they have had a really big feed they can go quite a while without eating. Is worth keeping an eye on his bowel movements just to make sure he is passing ok. Plus remember at this stage their growth rate can be astounding so keep up your calcium/vitamin dusting as well.
He'll soon be growing nicely!
I cant comment on US phoenix worm suppliers but found these:
http://www.phoenixworm.com/servlet/StoreFront

Obviously I havent ordered from this supplier as I'm in the UK but sure anyone who has can give you feedback.