Try looking into Frank Clegg bags, although it may be out of your price range.
At the $500 mark you won't really find anything except Saddle Back Leather that will last +15 years and age well at the same time.
That's retail of course and you might get something good on Ebay for the price.
I too dislike SBL for various reasons and got my self a Frank Clegg briefcase. It's a very good briefcase isn't quite as good as an SAB, but
isn't too far off from SABs quality.