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

Factual Questions
1

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?

2

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

3

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.

4

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.