The world needs more good emulators, such as XMESS and MAME. But where do you get the ROMs from? Check out the internet archive with a good broadband connection!
Try the following links: https://archive.org/details/MAME_0.151_ROMs and https://archive.org/details/MESS_0.151_Software_List_ROMs for some ROMs.
There are probably more, if you look at the "software" section and if you also try the "search"
You are in the hall of the mountain king.