Good on ya for thinking of a motorcycle-related gift!! If he's not had this bike before, how about a repair manual? Not too expensive, but when you need one, nothing else does the trick, especially useful is the troubleshooting chapter. Does he have a good helmet? You can spend a bit on a good helmet, because that old adage still applies- "If you have a $10 head, get a $10 helmet." Spend a bit more, get a better helmet. And don't forget a spare face shield or two. One other item people frequently wish they had are gloves- not too expensive, but something his fingers will appreciate, whether off-road gloves to keep the brambles off your skin or insulated gloves to keep your fingers warm. Good boots are another good thing, something he'll be glad he had when he needs them. And don't forget, a lot of bikes need "special" motor oil, so maybe a five-liter jug of good oil will make him smile.
OK, now for a comment- if you're thinking of him, he'll be happy with just a hug because *you* gave him the hug. That's my unbiased, objective and unsolicited opinion. ... Be happy!!