I found these while perusing eBay, and decided to try them:
http://www.ebay.ca/itm/390638462871?...84.m1439.l2649
As the description says, you actually get six turn signals for $12.00, including shipping. I think they'll be a suitable DS light, because of the flexible stem. I have a couple of bikes that I intend to use them on, including an old six volt two stroke, after I change the bulbs.
Here's a shot to give you an idea of the actual size: