Which webcam should I buy?

I have an eight year old son that really wants to make a Lego brick film. I know that I need the ability to manually focus, but many of the webcams out there only advertise auto-focus. Logitech has a product - the C160 - that allows for manual focus, but it is their cheapest webcam. The also offer the 9000 - but that is $70.

Has anyone used a webcam for about $30-50 that they liked? Logitech has the 250, 260 and 310, but no one at Logitech support can tell me if you can turn autofocus off.

What are you guys using? There has to be something in the $30 to 50 range, but I haven't found one yet.

Thanks for any help you can give.