If it's wooden boxes you're looking for, Arizona Silhouette has a selection of large boxes plus custom inserts designed to fit all the large pens (Gentleman's, Statesman, Emperor, etc.).
Regarding the "Regal" boxes from CSUSA...I recently received a flyer (I think it was included with a recent order) that advertised a "2007 Summer Closeout Sale" (30-70% off - Hurry, quantities are limited!)) and listed many, many items, including the large Regal boxes (now at $9.09 per). You might want to check out their website and see if they are still available.