Good question; I've been considering the same. Plano boxes stowed under the pedastal chairs is somewhat inconvenient.
My 2510 came with a little galley. I really have had no use for it. I've been thinking to tear it out and do some remodeling. If I was capable and had the tools, a custom cabinet could make for a multi-purpose storage area.
I'm interested in the storage centers you've priced; maybe you could post url to them?
Alternatively, I think replacing a pedastal chair box with taller one. It would have to be super sturdy and the pedastal height shortened.
Hopefully Pork-Chunker, John @ Madison CT, and et al can let us onto to their operation.