Me and OH are cyclists so my suggestions would be a pair of cycling glasses, the wrap around sunglasses ones, great in all weather not just summer as it stop's eyes from watering.
A mobile phone holder for his handle bars, that way if he wants to have his sat nav or strava on he can see it.
Inov8 do a really good waist pack, I've ordered one for my OH off Amazon, they hold all his essentials.
Cycling gloves, cycling socks, a good water bottle, probably got but always good to have plenty. I've got my OH an innertube toiletry bag, have a look at Cycleofgood.co.uk for cycling gifts.
T.shirts, cycling sports ones, or funny ones, I've ordered mine a Cycopath one with a bike on it, and a mug.
Not cycling, I've got my sons designer wallet, sat nav, holdall, overnight toiletry bag and smellies, keyrings etc.
Hope that helps