I picked these up a few weeks ago at Tuesday Morning (of all places).
I don't know if this style of brush is old news to y'all, but I've never seen them before.
I imagine they might be found in the Crafts aisle of your AC Moore/Michael's. I normally only visit that aisle for paints and sometimes varnishes. I generally get my brushes from the brush display in the Fine Art side of the store.
I just had to get them. I'm looking forward to trying them out.