But his form has attracted attention from higher up the League ladder, with a £750,000 price tag now put on the head of the 21-year-old.
Shrimpers deputy chairman Geoffrey King said: "He is not for sale. I had two calls within 10 minutes saying offers of £500,000 and £750,000 had been made.
"At that rate, it could have reached £1m. Neither offer had been made and, as I say, he is not for sale."
Eastwood himself has ruled out joining Forest, adding: "If I did leave, it would be for a Premiership or Championship side."