the only thing i can think of is to go to www.velotique.com. they have a bunch of computers and little pictures of the displays. the best option would likely be a one-line display-- multiple line displays can get pretty small, but as far as i know all the ones with the toys (meaning more functions) have multiple-line displays and therefore smaller numbers.

actually, come to think of it, velotique also has little stick-on bifocals for sticking on your sunglasses so you can read maps, etc. would that help? you could check out their section on sunglasses/prescripton compatable glasses anyway-- you might find something you could use instead. hope this helps! good luck.