C&G has them. Page 341 in their online catalog www.cgfordparts.com. A 48 piece set is $32. We don't use a lot o them. The last batch I bought from Drake didn't fit properly.
The instructions with the chrome acorn nut covers (if they include instructions) will tell you to either squeeze the sides together (like with a channel locks or a vise) to allow for a snug fit, or they will suggest silicone them in place.