There is a bucket feeder called a lamb bar. I have no experience with it, but have read about it. It is useful for several orphaned lambs and for people who have to go to work. Or you could sell him. Put him on Craigslist or take him to a livestock auction where they sell sheep and goats.
We had two bottle lambs this year. We put more money on milk, into them than what they are worth. Of course we fell in love, banded the boy, he will be a pet. Just can’t make ourselves sell them.
Good luck with your lamb.
We used to feed twice a day, that's really all they need. However, they do better on a free choice feeder, and we've switched to either putting out a bucket with nipples and filling it with cold milk, or a really large soda bottle with a pritchard teat with cold milk in it and letting them suck at will all day. The cold milk keeps them from overeating.