I broke a fin, and need to replace both sidebites 90kg what is a good standard basic fin to get please ?

Prowave 8'3

It would be a shame to limit the performance of a pro model board with basic fins.
Just get a set of Quobbas. For 90kg L fronts and a M rear is a good setup.

Why pay the price (both in money and technique) of a pro board and then limit its performance?