The 37-year-old is frustrated at a lack of first-team action at St Andrews and has recently been linked with a move to Celtic.
“It’s frustrating, I’m disappointed,” he told Sky Sports News.
“Who knows where my future lies, but if it’s elsewhere, I’ll look at it.
“I’m ready to come on (for Birmingham) and score goals if called upon.
“But the manager’s in the window for another centre-forward and if we can bring in a top-quality one, I’m all for that.
“I’m in no rush to go anywhere but if the right move comes along and me and my family fancy it, then yes, I would look at it.”
