Can't help ypu with a supply of pine dowels, but Axminster do a jig for making your own. The best I can remember is, its a steel plate with different size holes in, depending on which size dowel you want. The steel plate in mounted on a piece of wood with clearance holes in for the dowels to pass through. Cut some wood just a bit bigger than you need and knock it through the holes and you have your dowels ready for use.
Sorry can't remember its name, but it must be on their web site. Hope this is of help.
I bought a set of plug cutters in the end as I found only fluted pine dowels were available and that wasn't what I needed, at least now I can cut to fit the hole I need to fill instead of drilling the hole to fit the dowel. Thanks all