Hello @virap1 thanks for your post. You can certainly add a graphics/button and include a hyperlink that would take you to any website address. However, are you looking for that item to appear in the same shopping cart as other items in your Square site store? I do not think that would be possible. Customers would have to check out on that other site, wherever that hyperlink takes them to; it would not then add into their Square cart. You'd be mixing shopping carts and your Square site cannot do that. I hope this helps answer your question.
One option if you needed to keep one shopping cart in your Square store, is to add a new inventory item (that would be the other website's item). You'd then need to take care of purchasing that item yourself from the other website, and either have it shipped directly to your customer, or somehow warehouse the item yourself. I hope that work around makes sense, let me know if you have any questions.
