Comet Pinball has a "retro LED", frosted or clear. Frosted works best above the playfield and behind backglasses, and clear works well for below the playfield... "so I hear".
cometpinball.com
http://www.cometpinball.com/product-p/1retroled.htm
They also have discounts for 25 packs and 100 packs (check out the big buttons) which I found to be pretty nice if I was ever going to order from them. I'd say make SURE you utilize this as it is a nice discount for each pack, most pinball machines require at least 100 bulbs.
http://www.cometpinball.com/ProductDetails.asp?ProductCode=25-PACK-1RETROLED
http://www.cometpinball.com/product-p/100-pack-1retroled.htm
The answer you are going to get from 99% of Pinside EM enthusiasts: Don't use LEDs, they don't look good in EMs