Thats potentially a little challenging. Not finding warm boots, per say, as lots exist. But finding a pair that doesnt weigh more than you.
The Deemax Dry Winter Boots
You say hiking, so I assume you do not want the sort of bulky boot that are okay for snowshoeing and other activities. Maybe what you need is something such as Salomons Deemax Dry Winter Boots ($140). Theyre a hiking boot that uses a soft shell fabric to resist water and add some warmth. Thinsulate insulation keeps feet even warmer. And grippy Salomon soles offer good traction.
Take a look as well at The North Face's Slot GTX Winter Boots ($150). They have leather uppers with a Gore-Tex liner to keep feet dry. Primaloft insulation adds warmth, and the boots tall cut and flexible cuff is designed to keep out snow. Theyd work well as a winter hiker.
Of course, boots are just the start here. Be sure to wear the right sock combinationREI Silk One Liners ($7.50) would be great. Over those, SmartWool Mountaineer Socks ($23) for maximum warmth. You may end up getting boots a half-size large to accommodate the thick sock layer, and to ensure the boots dont restrict blood flow.
Top these off with a pair of Mountain Hardwear Xenon Stretch Gaiters ($85). Theyll prevent snow from getting into the boots and also shed snow so the boots stay drier and warmer.