Within the past year, I've gotten 2 B-12 shots from my Dr. (On request). He said my levels didn't really necessitate it, so my Insurance wouldn't pay for them, but he had no problem giving them to me.
Honestly, for me at the time(s), the perceived effects were negligible.
Had there been a decent perceived effect, I probably would have ordered some and done my own.
I may know of a decent spot, but I'll have to think about it....