What diacritics should be on "pho" (as in soup)?

I don’t have access to any Vietnamese advice or references. I tried doing a web search, but most websites leave it unmarked. Maybe that’s how it’s supposed to be, but I’m almost sure it’s something like “phô.” Can anyone help me out?

Oops, one more thing: I also have ‘bahn pho,’ which is what the noodles are called. Should ‘bahn’ have any marks on it?

Here is a menu page from a Pho chain on the West Coast. It looks like an acute accent, plus a curl off the top right of the o. I believe it is Unicode character 1EDB, described as Latin Small Letter O with Horn and Acute.

Thanks muchly, JohnM. It looks like I’ll have to leave it plain, as none of the fonts I’m using seem to contain the character needed. I see that the menu you linked to uses it unaccented in several places, so I guess I’m okay. Though, as a typography weirdo, I’d prefer to do it right.