"I want to play until I'm 40 and I'm only 34 now. I feel as fit as ever and I still feel like I've a lot to offer as a player," he said.
"I'm speaking to a few clubs (in England) at the moment but I've yet to hear anything that matches my ambitions."
The United manager Nigel Adkins is not keen to sell current goalkeeper Joe Murphy, but if a deal is struck, he may turn to the experienced Colgan rather than hoping Josh Lillis can make the step up.