Captain O'Sullivan had his penalty saved on the first attempt before the referee allowed him to retake the spot kick, after someone stepped into the box too early.
O'Sullivan went the same way but was denied by the keeper.
"We dominated the match. It felt like 70/30 possession, but we didn't take the chances," O'Sullivan said.
He said their defence was excellent on Saturday, including some great saves by goalkeeper James Towers.
"We had two youngsters playing at left and right back who came in for two guys who were out, and they played really well."
Ngongotaha have won two and drawn one this season.
Meanwhile, Rotorua United recorded a big win on Saturday at Neil Hunt Park against a strong Papamoa side.
United were relegated from the Waibop Federation One competition last season and are looking to gain promotion back into the top grade this season.
United striker Shadley Petersen scored goals in both halves on Saturday to help his team stay top of the Waibop Federation Two table.
His first goal came when the Papamoa goalkeeper and a defender had a mix-up and the ball fell kindly to Petersen's feet. He rolled the ball into an empty net to score.
His second came late in the second half after he finished off some nice build-up play.
Other top performers included United defenders Bryce Mckillop and Ash Gower-Rudman.
United will get their Chatham Cup campaign under way today against Matamata at Matamata.
