Andrew, in this area, we have a total split between the kinds of items stocked by plumbing supply sources. The home centers stock the more residential lines or get them from the manufacturer. The plumbing supply houses know that they can not compete with the big boxes on the cheaper lines, including Delta, and so they don't bother stocking them. They do have top-of-the-line commercial and architectural fixtures and there are several large showrooms in the area.
I suggest that you start looking for the specialty plumbing supply houses in your area. The first thing that you have to do is convince them that you really are willing to spend twice or more than you will pay for an off-the-shelf item from a home center. If you do that, then they will be more than happy to spend a lot of time looking for what you need. They still may not be able to find exactly what you want but they will want to find something that will fit your needs as closely as possible. One tip is that a recommendation from a plumber or a decorator will help you a lot. You and others may not like this situation but it is what has evolved in the market. Believe me, the plumbing supply houses do not like it either--or the volume manufacturers that have allowed this to happen.