He will want the following accessories pretty much as standard on any Adventure bike: Auxillary lights, skid plate, aftermarket metal handguards, waterproof panniers (saddle bags), crash bars, and side stand foot enlarger.
Auxillary Lights: Cyclops adventure Sports, Denali, or Clearwater
Skid Plate: Black Dog Cycle Works, Alt Rider, AXP Racing, or Outback Motortek,
Handguards: Barkbusters, Acerbis, KTM Factory (do not come on bike), or HDB
Waterproof Panniers: Mosko Moto, Lone Rider, Givi, or Nelson Rigg
Crash Bars: SW Motech, Outback Motortek, or T-Rex Racing
Side Stand Enlarger: Any brand as they're all about the same