Is there anyplace I can order a funnel that must fit into a 5/16" hole. I have trouble refilling my fancy olive oil bottle and spill it often

It is possible to make something that works too, like a piece of paper or foil curved and taped into a cone with a tiny opening... then it can be tossed afterwards? Or if a funnel isn't possible maybe pour it into a small watering can or a clean plastic squeeze bottle that has a screw on cap first and use that to fill your bottle? Just a few thoughts...