Just about every gunsmith involved with 'tactical' rifles will do a good job on your bolt but one of the most experienced is still GA Precision.
From their website:
Badger Ordnance Tactical Bolt Knob - installed, Remington 700 [Hide Details] $95 Oversize bolt knob allows fast, easy access to bolt even with gloved hands. No more holding the bolt handle with two fingers to pass the scope bell. The extra size and length gives unparalleled control of the bolt during cycling. Provides extra leverage for stuck rounds. 7075 T6 Aluminum alloy to keep the weight down and a Mil-spec Hardcoat anodized finish to last a lifetime.
Read review on Snipercountry.com [Click Here]
Services - GA Precision