I would steer clear of Burton. Their widest board is the Mayhem Wide 165 @ 26.8 waist width (there is no profit in supplying Sasquatch specific boards). This would be good for a 13, do-able on a 14, toe drag city for a 15. Shoe sizes increase by a 1/3" (~0.8cm) per size. Most people recommend about 25.8-26.0cm for a size twelve. This would mean you should ride a 26.7(13's) (I can vouch for this), 27.5 (14ís), 28.3 (15ís) (ouch!) to completely eliminate toe drag. You could subtract like 0.4-0.5 from these #ís if you set your stance past like 24Ē, and duck out past 18 degrees. You could ride slightly narrower than this even if you stay away from really aggressive carves. Iíve been thinking about making a separate thread on this subject.
So I think you should be looking for something in the mid to upper 27cm range or into the 28ís. This really limits things. I have scowered through 45-50 companies and only found these:
Many of them would be hard to find:
Donek Delrossi 175______w/ 29.0cm waist (probably way longer than you want)
Elan El Grande 167______w/ 28.4
Donek Sasquatch 170 ? _ w/ 28.0
Venture ______________ w/ 28.0 (Any Board)
Nitro Magnum 168 _____ w/ 27.8 (165 w/ 27.4) (gunslinger or warpath)
Voelkl Boostre 168 ____ w/ 27.5 waist
Elan Crest Wide _______ w/ 27.4
Nitro Sheild Wide 165____ w/ 27.2 (Venti or Tigre)
Nitro Pantera Wide 169___w/ 27.2
Option Redline Wide 167 w/ 27.1
K2 Format Wide 165 ____ w/ 27.1 (My Board!)
There are many other boards @ 27.0 and below. And I agree with arsenic0 that the Roundhouse would be awesome.
If you rock a full forward, semi-alpine stance you could go narrower.
Check out Nitro and K2, they have the widest lineups overall, Never Summer also has very wide options.
I posted a larger list of wide boards on an old post(2nd page), most of the boards listed are the longest available size. You could go shorter, but the width also drops: