I don't believe there is a number for that......I'm pretty sure it goes under the category of "custom". If they have any extras you'd have to call them to find out.
338 RUM dies will work for the Edge but I would recommend the tapered expander button. I've used both and there was no difference.
Not sure of the availability of Forester products in AU but you can buy a 300 RUM die from them and they will (for $10 or so) cut it to a 338 Edge.