I hand bead the majority on jewelry wire...the gauge depends on how heavy the box (and potential contents) will be.
You can buy the handles from a company called UMX or UME...something like that. Do a google search for the name. Or perhaps you could use drawer pulls...there's a zillion options.
The main problem that I've encountered is the closures. If the box has a good closure then I keep it. Otherwise, you'll have to find other options, i.e., hasps or latches from the hardware store or beads or buttons and elastic.
Be sure to use several coats of lacquer, either sprayed on or painted on...
I've found that good old Elmer's glue works to hold the lining in. And you may want to glue a small mirror just inside the lid, especially if there is a tear in the label. But I much prefer the label to any fu-fu stuff!
The main thing is to be creative and have fun! I sell them here and there if someone really likes them, but I mainly do it as a hobby for self gratification, you should see my stash!
I have a different, and very unique purse for everyday of the month (or several months)! And I'm stopped several times a day while carrying one.
Good luck and I hope you make a fortune if you are selling them!