Don;t know if it's too late for you... these are considered to be excellent
at Comtpoir Abel - they are known for them, and my friends enjoy them here.
I'm always disappointed every single time I try them in whichever restaurant! so it is a good idea to do some research. But if you wanted to try them for lunch, you really couldn't go wrong by going as vacapinta said to the cafe Giraudet by Place Bellecour - they serve mini quenelles and you could try different flavours with different sauces, as well as the traditional.
Hope this helps.