Well it stinks to high heavens to start with. I hate working with horn.smells like burning hair when you are working with it. Plus finding it in great thickness can be a problem. It is commonly seen in German guns but I’d rather not use it at all. Much rather use a Silvers pad or leather covered pad.
How, exactly, is this the OPs problem? He asked who he could PAY to have this work done, presumably, any craftsman who takes MONEY in exchange for fitting a horn buttplate will have made his peace with the smell. Horrible buttplate material? How so? Good horn takes checkering well, and looks like a million bucks when polished on the edges and fitted. It isn’t terribly heavy, is pretty durable, and lends a finished look to the end of a stock. Ebony does as well, but, is getting harder to get every year. A 3/8 block of checkered and polished horn, would look perfect on a gun like that. Much thicker than that might not look as well.
Opinions are like aholes, and there are lots of them out there, but, I would do lots of things prior to putting a chunk of plastic or rubber on the end of a gun.
Totally last resort.
Last I heard, this guy is still at it:http://dutchmanwoodworks.com/services/