Looking for a damn solution! Need to sell by weight or units. Help please.

Guys,

I am looking for a solution and can’t find one
I though it was simple.

So, I would like to create a grocery store to sell meat and vegetables using any ecommerce platform.

My client wants that the visitors would be able to buy products by units (e.g 5 tomatoes) or by weight (e.g 1.5 KG of tomatoes). It should be applied for all the product or most of them.

I have tried the extension Measurement Price Calculator of woo commerce (but that’s not the solution).
It works fine cause I achieve to have a “weight” field where customers can enter an amount and it is converted into money. But I can’t find a way to have both options at the same time, weight field and units field! (woo commerce told me there’s no way.)

Anyone knows how to achieve that?
either with a theme in the theme forest store, using magento, or prestashop or shop?

Thank you!