I want to add custom size input among my product variations

Hi!
As I wrote in the post title, I want offer to my customers the choice of input their custom size (actually I’m offering two sizes for my products, I manage the sizes with the variations).
Is it possible with some plugin?

I found this one: https://woocommerce.com/it-it/products/product-add-ons/
It does what I’m searching? There’re also other ways to do that?
Many thanks