Two letters denote a single sound? How about...
...Four. "Bought". From an Australian point of view that'd be the same as b-awe-t. But a generic American-accented 'bought' would be more akin to an Australian 'bart'...or, hmm - actually you're quite right:
Ah, fuck knows how to express this shit in words.
(That'd be an lrpd candidate if the lrpd hadn't taken a vow of non-potty-mouthedness...)