(Don't blame me for this silliness, XCthulhu asked me to...)
If you have MultiKey mapped to some key, an *NIX spelling would be:
MultiKey-^-o, MultiKey-?-?, MultiKey-^-o = ô¿ô
(You may need to repeat the circumflex if it's used combinatorily).
(OK, this is getting pretty silly. I promise not to participate in anything like this anymore. =)