Add-on while it is in the cart
When to use: Offer one relevant accessory or consumable when the customer already has the main item in their cart, framed as a finishing touch rather than an upsell.
Nice pick on the [Main Product]. A lot of people pair it with [Add-on], so it is ready to use right out of the box. Want me to add it for [$XX]?
Quick tip before you check out: the [Main Product] runs through [Consumable] over time. Want to add a [pack/refill] now so you are covered for the first few months?
One thing that goes really well with the [Main Product] is the [Add-on] for [$XX]. Totally optional, just easier to grab it in the same order. Should I add it?
If they say yes: Done, the [Add-on] is in your cart. Anything else before we check out?
If they say no: No problem, leaving it out. You can always add it later if you change your mind.