I also second the recommendation to buy rolls, especially for Shabbat lunch.

I keep odds and ends of challah in my freezer, and use them to make fresh bread crumbs, rather than buying. It only takes a few seconds in the food processor, saves money, and tastes better!

I also concur with the idea of baking one’s own challah to customize the size of the loaves. Lately, I’ve been making a large batch of challah dough using a 5-pound bag of flour. Then, I make various sizes (large, medium, and rolls) and freeze the already-baked challot (double-wrapped in the freezer). That way, I can defrost whatever size challot are appropriate for that week, without having to bake fresh ones every week. And if you warm them just before dinner, no one knows can guess that they are not freshly baked.