I got the "official" Rigol bag for 55 dollars from TEquipment. And I'm glad I did. It's more than just a "bag", it's actually a semi-hardshell case, with perfect fit, padding, compartments with room for the probe sets, manual, cables and some "etc". The quality of the fabric, stitching, zippers and clasps is excellent and I like the fact that it has an extra retaining strap inside to hold the scope in place even if the lid is open for some reason.
No, I'm not a salesman for Rigol, I'm just very happy with the bag!
(Sorry about the light...)