I can't find challah or brioche bread at any local bakeries and the only one that has ran out. I need the bread by today! Are there are similar breads I can buy at the grocery store or local bakery that would be fine instead?
It depends what you wanted to use this for. But both brioche and challah are more eggy/chewy than other breads. So a softer bread/roll would be a good substitute. If you live in an area where there might be a kosher butcher shop, you could probably find challah bread there
Challah bread in a kosher butcher shop. Challah can be found in most bakeries, bigger supermarkets, trader joes, whole foods...
A Chinese pai bao/pai pau ("row bun") is soft and chewy, and might be a good substitute. It has no egg in it, though. You can find these in Chinese bakeries, if you live by a Chinatown.
Potato Rolls or bread would be a good substitute.
Just ask for any enriched white bread at the bakery counter... That's ultimately what you're after.
Brioche is a rich dough, so alternatives could be other rich doughs such as: baba/savarin, kugelhopf, hot cross buns and even panettone (although that has extra extra flavour and is more like cake). It really all depends on what you are using it for.
You can bake challah/brioche at home with Voilà! Hallah Egg Bread Mixes from Tribes-A-Dozen.
For which recipe?
Kings Hawaiian is what I use.