Or you can use the larger mount boxes, and pig-tail down to the size that will fit in your receptacle. This is what my contractor did for me, reducing my 6 gauge to 10 gauge, which should fit in any higher quality receptacle (FIM in my case). Oh, and it does meet NEC code. This is done everyday, in every home that has 3 way light switches.
Hope this helps!
Brian
Hope this helps!
Brian