One thing that I noticed in the Vitamin Shoppe in the US was that in every section there were products available from the brand Solgar which was quite encouraging as this brand is readily available in my home town and one that I have been using for sometime for a variety of supplements.
My advice on getting your hands on the supplements that you need is to use all sources possible to get the right things at the best price. This may mean a little bit of forward planning and buying a few months supply. I find Amazon to have a great variety and good prices from their various vendors so if I or a friend is going to the UK I will order a decent supply to keep me covered. When I came back from the US I brought over 15 bottles of supplements back with me, this was due to way better prices over there and they also have a broader range which is sometimes not available locally. Another option is working with your local pharmacy, I have found that they are often able to get stock of certain supplements if you push them a bit and give them a few days to get their act together.
So spend a bit of time shopping around locally or on line to make sure you get the right supplements that you need, in good supply and at good prices. Remember supplements are like food, without them your performance will be affected, our food does not always deliver everything that we need in our diet!