Is there a case for the SP3 with a compartment for4 the pen? I don't like to attack it to the type cover. It seems me a pretty good idea however I can't find a case with this slot.
In that case i'd personally just get on amazon and find the cheapest (pretty hard to mess up a neoprene sleeve) sleeve/pouch for a 13" laptop that has a zip pocket on the front. Much easier just to search for a 13" macbook air case than a surface pro 3 case.