What exactly is your price range? How large of a blade? I assume thick and wide, but how long?
Just off the top of my head I'd say a Spydie Para-Military, but you said he doesn't like those. So what else... It's not flat grind, but I'd imagine it cuts very well being sort of a high hollow grind I suppose. A Benchmade 710.
Also, again not flat grind, but a Zero Tolerance 0200 should be quite robust and a great heavy duty knife, and you could have Tom Krein make it a flat grind... but I've no idea what he charges. The ZT 0500 MUDD looks to be a flat ground to my eyes.
What about a nice smaller fixed blade like the Benchmade Activator?