We have for sale a Blatz Old Heidelberg tap knob. It has white lettering on a blue and red background and has "Milwaukee" at the bottom in brownish gold lettering. The front of it is about 1 5/8" wide. The body of it is silver and BLATZ is embossed in the back.
Other ones I've seen have a "neck" on the bottom which probably originally connected to the actual tap handle. This one is just the ball on top.
Flat shipping fee of $7.50 in the US, eBay international shipping for overseas buyers. Local pick up available near Madison, WI.