You can true a nipple or true a Topolino wheel just like any other hand built wheel. The only problem it trying to keep the spoke from twisting while you get it to the right tension. I generally use a pair of padded pliers to hold the spoke at the molded plastic end.
You can even use a standard nipple. The ones Topolino uses weigh a gram less each, or almost an ounce a wheel, so they make a difference when all combined.