What size bonding jumper for 200 amp service panel?

There is no bonding jumper wire required on a 200 amp service panel. The meter stack is metallic and is continuous from the mast head down to the distribution panel.

If you are talking about the ground wire for a 200 amp panel it requires a #6 bare copper conductor that connects the grounding rod or plate to the neutral point in the distribution panel.

Assuming the answer above is an example of a service, where the meter is stacked above the first service disconnect and is mated to this panel by a threaded hub. However if your meter were to be mounted beside your first service disconnect and a metal nipple with lock nuts were used for raceway. You would be required to have a bonding jumper on that nipple sized according to NEC Table 250.122. So for 200 amp that would be #6 copper or #4 aluminum.