You can get 11 and most any bore wads, card, fiber and overshot thin B wads from trackofthewolf.com. If you go to their web site and click on ammunition and go down that list, or this: http://www.trackofthewolf.com/List/Item.aspx/171/1

They list wads from .410, then 28, 24, etc to 4 bore.

One of the nice things of their listing, is they give the actual diameter of the wads, which is always oversize to allow for compression - ie: tight fit.