Stocks can be ordered toll free at (866)776-9292 from H&R, or you can snail mail an order form to them if you have one. Supposedly we should be able to place orders online at the H&R store thatdisappeared from their website for upgrading, but that hasn't happened yet, I suspect they're waiting to get their system in order in Ilion before that happens. Stocks can be installed/removed at home, see the FAQs to learn how.
Tim