Are you saying that you couldn't find any 180mm Gyutos or didn't find any that you liked? If it is the former here is a link: http://www.japanesechefsknife.com/HDSeries.html.
A Kramer is similar to a very thin Nakiri with an even thinner tip. The Nakiri has a long relatively flat edge. It will have more of its edge in contact with the board then a larger Gyuto. Typically there are also thin knifes, so they will easily glide through veggies. The lack of a tip is noticeable when trying to trim proteins or following the curve of a round fruit. It can be done, its just a bit awkward.
A larger version of a petty, would be a Sujihiki. There are available in 180mm.
Improved suggestions could be made, if there was a better understanding of why you are looking for a larger heel, is it for knuckle clearance, wanting a chopping knife or ...?