I actually would go to Lowes if there was one as close as HD.... I don't ever talk to the employees at any of the stores, unless I need to find something.
It's just a little ridiculous to not have any of that part left, good thing it's not a critical piece for me.
Sureeeee.
I bought it at HD, it's a dremel bit. As far as tips, be prepared for a long process, it is very very slow. I also would not have cut my overflow as deep if I were to do it again. It helps if you have someone to spray spray spray with a spray bottle, otherwise find a way to have water on the part you are cutting nonstop. I rocked the bit to get it down (hope this makes sense). I would tilt it, then put it upright, and continued to do this over and over. Another small thing, when I got towards the end, I finished it from the outside in, to prevent chipout. Let me know if i need to clarify anything.