I have a group of 8 wishing to take this. I found the tours out of Inverness but not Edinburgh. Are there any companies doing this out of Edinburgh?
http://www.mini-tours.com/day_tours/tour_western_highlands.htm
done a wee bit of a search for you and found this company, can take up to 8 people and can adjust the tours to suit you. I have no idea of cost but a quick email to Craig and you should find out.