JTT, as you and Bill D infer, trying to indicate sound merely by using other words that have a 'similar' sound is not very sucessful. That is why most dictionaries use symbols for phonetic sounds.
We may have learned one of these schemes in school, but they are easily forgotten, and html doesn't help to reproduce them in a post.

For the sound wanted here, Webster's uses bo, with a macron (little dash) above the o. Unfortunately, this is hard to reproduce in a post. Words using this convention for the sound are beau (but not in the south where it may become 'bew-fort' in Beaufort), bogle (ghost), bow (as in a hairbow or bow and arrow but not as in the bow of a ship or a curtsey)---, etc. etc. etc.

The Oxford I have also uses bo with a macron over the italicized o.

Gates and the other wizards who devise computer programs, being short on literacy, have not considered these problems.