Does anyone have experience of how I can purchase an item from Ebay which is not advertised on there, as it's a part from a vehicle thats being broken for spares

all thats advertised on there at the moment is a wheel nut

I wish to pay using Paypal, which after speaking to him on the phone is preferred by us both.
Will the seller need to advertise the item with a 'Buy It Now' or is there another way

He's happy to pay the charges.
Chris.