You might try going to bead stores in person and checking out there Silver letters beads. The alphabet beads often have bigger holes that would accommodate the Pandora chain (I don't know how many mm thick the Pandora chain is). If you don't have a bead store locally, shop around online.
Here's an example of sterling Greek letter beads. They have 4mm holes, and are $1.59 a piece:
http://www.artbeads.com/alphabet-bea...ter-beads.html
If these don't work, there are tons of other sites that sell similar beads. Firemountain Gems is a good site but you usually have to buy 4 at a time.