Suit separates - good idea, as suit pants might require a recut (expensive and sometimes risky). Men's Wearhouse, meh. Jos. A. Bank sells suit separates, but apparently he might not be open to an old-fashioned cut like that. Brooks Brothers has more modern-looking separates, which coincidentally are on sale now.
Another option is a traveling tailor, who takes measurements instead of relying on the customer's skill at doing that (which is one reason online MTM can go so badly). Still, any tailor who wouldn't charge much for a suit likely isn't very good and might have trouble making a modern-looking suit that flatters a muscular man.