Buy a couple of this one 1/2" shaft and 2" diameter. Its dirt cheap for what it is. You could easily modify the corners yourself. Or let somebody grind it for you. basically you have to round them, take same amount from the back support.


And sharpening and resharpening could not be easier on this bit using 600 and 1000 grit diamond plate.
There are cheap plates, a bit more expensive plates and there are better expensive plates. Which both work. Here is the how to video

Anyway, the keyword is "bottom cleaning bit" . That's how the Chinese call them.