Look up “messenger bag”... Basically a briefcase with a shoulder strap. Yes, you can find them overly-fancy if you want to make a fashion statement. (ie. lean toward the man-purse end of the spectrum). Or you can find them in high-dollar leather, or you can go more rugged with canvas etc. I use one (Swiss Army) occasionally going too and from work. Less lately since I’ve been resolved to quit bringing work home with me. ;-) But when I have to carry a briefcase like bag to hold stuff, I like the messenger bag style (or backpack style) since it keeps your hands free coffee, keys, lights, knives, guns... Gives you options...
I have a messenger bag. Most are too big. I don’t need to carry much...just a PX4 Storm and a couple spare mags. 5.11 makes a perfect messenger bag, but it just screams “GUN!” because they only come in tactical colors. I got one anyway because there may come a day when you want to scream “GUN!” to keep the disillusioned Obama voters at bay once their entitlement checks stop coming.