I have several Montblanc bags, and while they are good quality, they are poor value. You will get the same craftsmanship from Picard, also made in Germany, for a much lower price. I bought my first briefcase in calf leather from them circa 1994, and it still looks new.

Otherwise Frank Clegg and Glaser Designs are great choices as well and they will make it bespoke for you.

Have a look also at this epic Styleforum thread