Desperate.com is a good source for the signs, but dropshipping through them would eat your profits alive -- their discounts scale up for quantity. This is a problem you'll find on almost any item that has a low retail price point -- dropshipping tends to have such low margins, that once you tack on the relatively high costs of shipping and handling (figure a minimum of $5 for packaging, postage, and man-hours consumed) that you're either selling at a non-competitive price, or selling competitive but losing money on the front-end orders. That's not always a bad thing, but you have to make sure you have something in the way of an upsell, follow-up offer etc. that can offset the losses you take on the front-end order.
Frank