Bowyer said: "Every player in the Championship is for sale. Of course, you don't want to lose them and they are not the finished article yet, they can both improve on certain aspects of their game.
"But they can do the hardest part, which is score goals."
Gestede has spoken of his desire to play at the top level and Bowyer said: "You want players who are hungry and want to improve themselves. You don't want players who are just happy to turn up for work.
"If I was to lose either of them I would have to find another 20-goal striker and with the transfer embargo we have that might prove challenging."