I have the Snugg Case which is real nice. Has a long slot on the side that allows you to carry the pen or even papers. No real dedicated place for the pen. The Maroo sleeve for the Surface 3 would be excellent as well if it matches the one for the SP3 which I believe it does. I also have been using a Tumi Medium Laptop Case which also has the space to carry other items as well. It gives a bit of extra room that can also accommodate the SP3 and has really become my primary carrying case separate of my actual briefcase.