See the 2007 Retail Parts price list page in the FAQs, H&R willl sell you any stock they offer, not all are listed, you have to ask for some of them by name. H&R doesn't make any of the synthetic stocks, they're all made by Choate Machine and Tool.
The Boyd's thumbhole laminated stocks are out of stock until early next year, you can see them in the "let's see some Handis" link in the FAQs.
Tim