How to add multiple items ?

Hi

Thank you very much for this plugin, it does wonders !
unfortunately, I can’t find a way to make it match my need :
whenever someone orders a product, I need to charge delivery (fixed amount) and therefore I would like to trigger the stripe checkout with multiple items (1 product + 1 flat fee delivery charge)
the price ID is tied to product but how can I tie to it to a “basket of price ids” ?
how can I do that ?

thank you very much in advance for your insights !

Michael