Gun Parts Corp has 10" models that were cut down from the longer 16" models, and claims to have the original 10" (not cut down) for an extra $10.
When I ordered the original 10" bayonet a year or so back, they sent me the cut down model. Don't know whether it was a mistake or they were just out of what I asked for (and they didn't mind keeping my $10).
They accepted my return with no objections, but I was screwed on the shipping both ways.