458RugerNo1,

Graf's has the .375" 300gr RN Interbond listed on their web site but it's listed as not in stock at the moment. That implies, at least to me, that the bullets have a part number and will be be manufactured but that Graf's just hasn't received any yet.

See:
http://www.grafs.com/shopProducts.cfm/categoryID/53/noSearchText/1

MidwayUSA also has them listed but it's listed as "Coming soon".

See:
http://www.midwayusa.com/rewriteaproduct/434193

I've had very good luck, accuracy wise, with the .375" 300gr Hornady RN Interlock so I'm looking forwad to the Interbond being available.

-Bob F.