I'd say the first thing is to assemble what you're going to put into the bag, on a table top, on top of a couple of sheets of newspaper. Try to arrange it from top to bottom on the paper as it would sit within the bag, THEN with a marker draw around the outside of the items. (Use about 3 or more sheets of newspaper on top of each other to protect your table top from the ink bleeding through - unless you're single and nobody will care if you mark your table top :shocked2: )
You will end up with an image of how big the interior of the bag may need to be, and be able to start there when looking for bags. REMEMBER that a bag made of two pieces of leather sewn together has less room than the same shaped bag that has a gusset sewn in to expand the interior. Your outline only gives you a 2D image of a 3D situation, so if you like the bags of simpler construction, you have to allow for the thickness of the tools and such that you place inside.
LD