Looking for a back rest to keep the Mrs happy don't want one myself so don't want to pay a fortune as it'll be only on for the "better" half when she comes out
I don't know if you are looking to buy new, but have a look at this company. http://europcustom.com/sissybars/triumph/sissybar_triumph_america_speedmaster They are based in Spain but their bars look better than the Fehling ones (in my opinion) and are cheaper. The manufacturer appears to be a company named Spaan. Some of their product are available on Amazon but not the back rest.
One here not that cheap though https://www.gumtree.com/p/accessories-styling/triumph-sissy-bar/1254554789