[Leica] Which flash for minimal use?

[myrmidons at me.com (Fred Bastiat)]

I have the M240 and 35mm and 50mm Summicrons. I like to combine business 
with pleasure so when I go to trade shows in far away locations, I need 
flash for indoor product shots. So maybe 30 or 40 images, and then I'm off 
for fun in the mountains or whatever, and then I have no need for flash as 
I'll be carrying a tripod.

I could just bring a Canon G12 for the trade show stuff. Or, I could carry a 
flash for the Leica. So, the flash should be no larger, and hopefully 
lighter than the G12.

So, what's a good, cheap, small, lightweight flash that will work with the 
M240?

Thanks!