There are some lights that mount to the trigger guard. Google it.
Aside from that, you'd have to add a rail. Not that hard to do if you have a Dremel, a good set of drill bits and a #6-48 TPI tap. Then you just buy a weaver rail kit for a Remington 700 and shape it to sit flush and level on your dustsheild. Get the light first, so you can make sure it locks in the right postition.
Edit: After you attach it, be sure to grind off the ends of the screws on the inside of the dust sheild, then peen them so they can't back out. Use threadlocker, too.