Check eBay for Kendal & Hyde or SALT Co. I have a briefcase by them (same designer for both). Defunct companies but the products are solid, heavy leather and I like the style. My briefcase has been on a hundred or more flights, international trips, tossed around, walked miles etc and still looks fantastic and has held up. I managed to get mine for $250 from a FB group that trades this specific brand.

If you absolutely positively got to have an expensive designer brand, then I'd look at Montblanc. They make good quality products and fit right in with a stylish lawyer aesthetic. The only downside to my SALT Co bag is that it is thick and heavy leather, so I've thought about retiring it and Montblanc is the brand I keep coming back to. Haven't actually done it yet because my current bag is just so good.