Turbine does not offer many of the legendary version perks for their expansion packs as individual items.
My personal opinion is that Turbine wants our dollars. Turbine only allows customers that are willing to spend the dollars the ability to get the perks. You have to buy the legendary version of the expansion before Turbine permanently discontinues it.
There is some hope that the +10 Quest slots for the fancy version of Helms Deep will eventually populated to the Lotro Store.
Unless stated otherwise, all content in this post is My Personal Opinion.