I used a lot of time researching good and reliable suppliers of leather, leathercrafter tools and accessories. There are many more suppliers than I have listed here, and some of those listed only supply retailers (like Horween - but you can buy their goods via i.e. AACrack), some of them have strange "online" payment systems (at least from a Scandinavian perspective - Royalwood is a good example). If you are about to start leathecrafting, maybe the most reasonable way is to try some of the starter kits from Tandy. Later on, when you get more experienced and know what you need (some people I know say they need only a headknife!) you can switch to some professional (and expensive) tools like those from Joseph Dixon or Vergez Blanchard.