It's really important to use calibrated glass cabochons to avoid any distortion of the image. I have not tried it yet, but I would imagine one could adhere a paper image underneath. I purchased these cabs from AliExpress, a China based online store similar to Amazon. I am amazed at the art supplies I can find there that I can't find anywhere else. The shipping time is anywhere from 14 - 45 days, but it worth the wait for the prices and many merchants offer free shipping.
The barrette is a 3 inch clip and it is currently listed for sale in my Etsy shop for $38.