I was interested in a single shot .410 as well, and I looked for a Winchester Model 20, which are beautiful little guns, but I found that they are pretty few and far between, and one in nice condition is not inexpensive.
I ended up with an interesting little .410 Belgian side-lever hammer folding single shot with a skeletonized, straight-grip buttstock. At 3 1/2 pounds it is considerably smaller and lighter weight than the M 20, and it is a very nice little gun. I am happy with it, but be aware that some of them are in pretty tough shape.
