Any number of fonts have vowels with macrons above. I don't believe I've ever seen one with precomposed vowels with macrons below -- not even sure they are encoded in Unicode. R & L with macrons below, yes, for transliterated Devanagari (Latin Extended Additional), but not, I think, macrons below.

So your best bet is to pick an Adobe OpenType font, or one from a foundry that allows end-user modification, make up the combining macron below, then make up the vowel with the macron below. If I'm right & it isn't encoded in Unicode, don't give it a Unicode value, just write a ccmp feature so the vowel + combining macron below calls your character.

This only works with OpenType savvy applications programs like InDesign. If you are going to use a Type 1 font & typesetting program, make up the characters needed, & lie about their names -- for instance, put one set in the spot where vowels with umlauts (aka dieresis) normally go, and pick another accented vowel for the other -- the grave, maybe? To set them, you will have to type (e.g., set) the umlauted vowel etc. but using your special font. Further use (aside from printing) of the typeset file will not be possible without editing, because you've called the "wrong" character.

Otherwise, you will typeset very slowly, using the plain vowels and the regular macron character hand kerned (& lowered for the macron below).

To be consistent with the Hepburn romanization standard, I would resist any suggestions to put the macron under the vowel. Sometimes it's done by adding an underline to those letters as a way of avoiding actual diacritical marks, but that is a typographical hack. Most fonts from the last 10 years have ā, ō, & ū. I imagine one would have to know what the show was before font recommendations could be made.

The macron will be going above the o and the u. It is a Japanese paintings show, 1615–1865.

Minion Pro has macrons over all vowels.
(So does Times New Roman, but you've put in a "beautiful" restriction :-) )

Yes, Minion Pro is what I have been looking at so far. Thanks!

You can also take a look at Warnock Pro (slighly more Palatino-esque) and, to name a sans, Myriad Pro. The magic word seems to be "Pro" ...

If you have or know someone who has any of the recent Adobe Creative Suites, you can check all of these out. They come with the package!

Wonderful, thank you!

A quick go-through gives me additional possibilities like Arno Pro, Bodoni/Didot (interestingly, my version of Bodoni includes ȳ, while Didot does not), Brioso Pro (not really a serif), Cambria, Adobe Caslon Pro, Century, Chaparral Pro, Constantia, Adobe Garamond Pro, Hoefler Text (albeit with an odd, semi-rounded macron that looks strange), Adobe Jenson Pro, Palatino, Trajan, etc.

As Theunis said, any Adobe Pro face should have at least the five basic vowels with macron above.