The forward joined Notts for an undisclosed fee from Hartlepool United in May 2017.
A graduate of Oldham Athletic's academy, Alessandra has amassed almost 350 career appearances since his debut in 2007.
The Manchester-born frontman scored 25 goals across two seasons for Plymouth Argyle, including 13 in the 2014-15 campaign as the Pilgrims made the League Two play-offs.
Home kit: Mac & Richard Gill
Away kit: Mac & Richard Gill
Third kit: Available
Boots & socks: Available