I bought a Snugg case for my Pro 3 and it fits nicely.
http://www.amazon.co.uk/Snugg-Micro...8&qid=1405782494&sr=8-3&keywords=surface+case
Doesn't add too much to the depth (still slides into my shoulder bag) and I can flip it closed and the magnetic catch holds it shut. This is a link to the
Amazon UK site. I am pretty sure that Microsoft US are selling these cases, and in fact I that it is also marketed on
Amazon as a case for the 13" MacBook.
I also bought a Microsoft Bluetooth wedge mouse to go with my SP3 and it works ok. It's a nice small mouse but after having used it for a few days, I kinda wish that I had looked for a Bluetooth mouse which had a scroll wheel in it. The up-down touch-slide function on this mouse seems to often have a slight delay in registering the presence of my fingers and the fact that I am trying to get it to scroll up or down and then suddenly it does realise that my fingers are stroking the top of it and sends the screen zooming up or down very fast and goes flying past the point that I wanted to reach. Might have a look to see if it is possible to adjust the sensitivity settings on it, but overall it's not a bad little mouse and means that I can have the USB port free.