Spare parts for MZ are easy to get, at least here in Germany.
I would not sandblast the chrome, it will be a pain to get the rough surface plain again for rechroming.
To rechrome the exhaust will be difficult due to the carbon inside, the platers here will not rechrome any exhaust parts if they don't have the chance of cleaning them by themselfs, (to sandblast the inner side as long as you reach might work, but is it worth it), the hole unit have to be cleaned in several special cleaning baths.
The exhaust is a big part, so rechroming will cost some money, it would be cheaper to buy a replace, (at least here in Germany with 19% tax):
The adress above is a good ressource for any other parts too.
Here a photo of the factory and the sign near the ´street to the factory made in 1990 a couple of minutes before we went out for test ride: