How can I get my toddler to give up the bedtime bottle? He has a hard time going to bed otherwise.

Just give it up. You are the one having trouble giving it up. Give it up, you already know it is not a good thing to continue. Usually your toddler will learn very quickly and adapt to the new routine you create (no bottle) be strong don't give it back , it is for his own good.
Put water in it. To promote change you need to remove part of the reward for getting a bottle, the sweet taste of the milk.If he gets his bottle, but it is boring, he'll eventually toss it. If he loves a water bottle, at least it won't rot his teeth.