I'm not aware of any aftermarket pins like that. You can get hollow roll spring pins from most hardware stores. But I think the smallest available is 1/16" diameter and length of those seems to be limited to 1". That's not long enough for a barrel pin.
Are you using a flat face pin punch to remove the pins? Trying to tap pins out with a pointed object can lead to trouble.
On a side note, most guys with long rifles do not remove the barrel from the stock on a regular basis. Floor wax or bees wax is used to seal the gap between the barrel and the stock to keep moisture out as much as possible. And the barrel is cleaned while still in the stock.
I tend to get a bit sloppy with the soap and water when cleaning my guns and usually protect the barrel/wood gap with a plastic umbrella bag as shown in the cleaning tip I posted in the reference forum.
http://www.huntingnet.com/forum/blac...aning-tip.html