I have a 2004 Audi A4 1.8T and live in a state where you must have
both front and rear license plates. I have attached the rear license
plate with the screws that were already there. There is also a spot
for a front license plate (protruding), with 2 screw holes but no
screws.

I have tried using the screws from the back license plate to hold the
front license plate, however they do not fit. What would be the size
of the 2 screws I would use to attach the front license plate to the
protruding license plate area, and where would I find such screws
either online or at a nationally franchised shop?

Thanks.

Wouldn't your Audi Dealer have these? :) It's probably worth a phone
call... Even still, a millimeter measurement of the diameter of the
holes, brought to your favorite hardware store, and some nice person
will be glad to help you. Or your local auto parts store ... But,
exhausting all of those possibilities, you'll still have to go to one
of those places to get the screws...

I am not a GA Researcher.

Usually license plate screws are 1/4" diameter, and you can buy
plastic backings to screw the screws into.

http://www.acehardware.com/family/index.jsp?categoryId=1258991