Rio Grande Games replied a few days later. By all accounts, they hadn't put any mark-up on the quote, that was straight form the manufacturers. All they could suggest was that I tried another source, such as the makers of Dice Forge. (Which I have already done, also a 'no')
So it's quite literally 'back to the drawing board'. The thought of having to design my own dice doesn't feel me with any warm thoughts.
However, there is more than one way to randomize. After two hours of crushing depression, I'm working on an alternative solution suggested by Shem. Once I've got a working copy, I'll share more on here.