Any bike shop will be able to supply thick contact sheets in most of the colors required including clear. Common brands are One Industries or Factory Effex. Usually 3 sheets per packet, priced $30-$40. Or they will be able to organise pre-printed with your race number, name & sponsor logo's if you wish, from between $90.00 to $120. You just have to measure the height & width of the oval and pick your numbers & colors. We do it all the time through the shop, and usually use Decal Works. About 10 days wait ex USA.
Cheers,
K