There are plenty of alternatives:
Jackson Martinez from Porto
28 years old
Strong + Pace
92 goals from his last 132 games (0.69 goals per match)
Edinson Cavani from PSG
28 years old
Strong + Pace
94 goals from his last 134 games (0.67 goals per match) + he has been forced to play more on the wing at PSG to accomodate for Ibrahimovic as main striker but at Napoli when he was the main man he was a consistent 30+ goals a season striker
Christian Benteke from Aston Villa
24 years old
Strong (perfect target man and PL proven)
49 goals in 99 games (0.5 goals per match)
Mauro Icardi from Inter
22 years old
Strong + Pace
Breakthrough season this year and he scored 27 goals from 48 games (0.56 goals per match)
Mario Mandzukic from Atlético Madrid
29 years old
Strong (hardworker and perfect target man)
68 goals from 130 games (0.52 goals per match)
Carlos Bacca from Sevilla
29 year old
Pace
49 goals from 106 games (0.46 goals per match)
Gonzalo Higuain from Napoli
27 years old
Strong
53 goals in 102 games (0.52 goals per match)
Some ok options but none get me particularly excited. I'd prefer to play Hernandez than half of those.