In my experience, you can find pushers on eBAY from time to time, albeit they are not cheap. $100 ea. on average. Also, you have to make sure they fit. Best to have your qualified watchmaker give you exact measurement of what you need. There may be a member here that can also tell you from experience.

Below are a few examples, but I can not tell you if these will fit your watch. I am using as reference for you to see how the pusher is set-up.

Here is an example of pusher head only:

http://www.ebay.com/itm/Original-Heuer-Autavia-Drucker-Pusher-NOS-fluted-geriffelt-/181643829950?pt=DE_Kleidung_Schmuck_Accessoires_Uhren_Armbanduhren&hash=item2a4ad0e2be

Here is an example of the whole unit:

http://www.ebay.com/itm/Original-Heuer-Autavia-Drucker-pushers-NOS-/181643830369?pt=DE_Kleidung_Schmuck_Accessoires_Uhren_Armbanduhren&hash=item2a4ad0e461

Once you know, you can also post a WTB and see of one of the members has the proper size you are looking for. To me, yours doesn't look too bad. If you are set on replacing, try polishing first and see if the result is acceptable. you don't have much to lose. I do not believe these are plated brass, but again I defer to the more experienced population out there.

Good luck.