The winger has yet to confirm where he is playing next season.
He told the Shropshire Star that dialogue between player and club officials continues.
Newby played a key role in keeping the Bucks in the National League North last season.
Their new manager Cowan knows how good he was in the final few months and confirmed to fans that he is wanted for 2018-19.
“We’ve got to find something that suits Elliot and suits us,” he told the Star.
“We know he is good enough, that’s not in doubt, but we’ve had a few conversations and talks are ongoing.”