NES Emulator with Video Mirroring?

Hi all!

I am trying to find an emulator for PC with video mirroring because I want to play sidescrollers from right to left as a challenge. I have found some that will flip horizontally AND vertically at the same time, but am only interested in them being flipped horizontally.

I have tried about 8 or 9 emulators with no luck. Does anyone have an emulator that they like that can do this? Alternatively, does anyone have any suggestions that don't involve playing while looking at a mirror?

It is important that I beat Mega Man 2 playing right to left! Please help me!!