First question is it signed? That puts the value up a fair bit.
Doing some looking, I found that a Alonso 2010 Ferrari visor is worth £349.99. I would think a Verstappen first win visor would be worth similar.
I would consider perhaps holding on to this exceedingly rare item, it was used in his first win and if he is a legend someday (Schumacher-esque perhaps) a visor from his first win could be worth thousands.
It is a special item people will want, I’m sure that if you do want to sell it (I would not personally), I’m just assuming you may, it would not be too hard.
Congratulations on winning the visor, it may be an especially special piece of F1 memorabilia in the future!