Some single blade sight blanks are available at TOTW - point blank + 1 leaf). You could a search for Express Sights on google and you'll come up with some very cool sights - perhaps like my 3 leaf + standing point blank sight.
; I should note here that most express sights have a standing sight, + any number of leaves, therefore a single leaf sight actually has 2 sights, 2 leaves has 3 sights, etc, as the leafs stand up in front of the point blank sight.