Creating a free sample cart in wordpress shop

I would like to explore possible solution on how to create a button on the product page to say Order free sample and then people can order free samples from the store without seeing prices on the cart page etc.

Right now I had a developer modify the add to cart button to say ‘add samples’ and then code in to remove the prices. This is not working as now I cant update many on the plugins or the coding will be lost. Its only a matter of time before I will need to update this plugins. I dont think this is a smart solution. Any ideas are welcome. Many Thanks, Ali

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