Oh, Bellamy's was a real hassle sometimes to get. I was actually annoyed with myself that I chose such an elsusively available formula for my baby.
I rarely got it from B2B, mainly because I rarely go there and the few time I tried (after one successful try) they were out of stock.
I sometimes got it from Three Sixty, who also ran out all the time. It's also available at some PnS Internationals, but at a higher price ($40 more).
The most reliable distributer is BabyCentral, the online baby shop. They always have it in stock, prices are ok, and they deliver. I would just stock up when I made an order.