For buying things like haybags, halters, leads, vaccinations, etc. I recommend Useful Lama Items. Some things they have will be cheaper at your local feed store so do check prices and local availability before you go hog wild online. Another great resource for medication, wormers, syringes, plastic gloves, fly control products, etc. is Jeffers. Both the equine and the livestock departments have items we use. Valley Vet supply is another resource for wormers, medications, and supplies.
We use Norm Evans, DVM formulated minerals. Dr. Evans' Book, The Veterinary Field Guide to Llamas and Alpacas is an essential reference that we use several times a week. I've heard that it's out of print right now so I will let you know where to get it as soon as I find out.
To learn more about handling and training your alpacas, we recommend Camelidynamics. For halters, this is the kind you want! It's really important that your halter fits your alpaca properly. If it slips down onto the cartilage just above the nose - THEY WON'T BE ABLE TO BREATHE! So make sure it fits tightly around the head, up by the eyes rather than down on the nose.
If you are expecting a new cria to be coming soon, you will want to have some plasma available in case he/she needs a transfusion. This will be a plasma transfusion given IP (in the gut), rather than a blood transfusion. It is important to have a bag of plasma in your freezer in case you need it. You can get this from Triple J Farms. In case their website is confusing, (I found it so since I am not a vet) just call them and tell them you need some lama plasma. More on this when we talk about cria care. Or leave questions in the comments section and I will answer them.
**FYI: When you see the word "lama" it refers to both llamas and alpacas. The one "l" instead of two means that they are talking about both types of camelids.**