Have you checked out any of the options for skiing? Several options there for disposable hand warmers (1 example: https://hothands.com/ ). I use the Hot Hands and can comfortably hold ski poles as though nothing is there.

Then there are things like Milwaukee’s battery heated gloves, but the battery may be heavier than you care for for long rides.

Good luck - my wife’s hands freeze immediately in cold weather, but she likes the Hot Hands for her skiing and winter running.