It's actually not such a lame question...I was in Japan earlier this year and I saw a few bikes that had an aftermarket clamp on their handlebar (or stem?) that held an umbrella. Most Japanese bike commuters only go about 7-10 miles an hour and just hold their umbrellas, so this clamp actually seems like an interesting alternative.

Here's one from Taiwan (although different from the one I saw):

http://cgi.tw.ebay.com/ws/eBayISAPI....ayphotohosting