I saw a series of Remmington 1100's from .410, 20, 16, 12, and might have been more, they wanted about $6000 for the set. all matching and all in mint condition.
I was looking for a .410 for my girlfriend. she is small framed and doesn't have enough weight to handle a 12gage, so Ifigured I'd start her out on something smaller.
Since I' am looking for one as well, I'll see if I can point you to them as I find one.
the last one I saw was in the $600 range and was not in great shape. They are not common. But I'll let you know.