Palo Azul can be bought from around $1.49 per pack and it has 3 or 4 little pieces of wood. Palo Azul stands for Blue Stick. Dont anticipate on seeing a blue piece of stick or the wood to be color blue. That is just the name of the wood that is heated with water and you drink it. Its a standard piece of wood of a certain tree that extracs a tea like substances. Also, be aware that since you are drinking extracts from a piece of wood, the taste is going to be (I dont want to use the word unpleasant but the taste will be ackward) different.
Your best bet is to find a Mexican store that sells spices or try your local convinient store see if they carry them on their spice section.
This Palo Azul can be bought a lot more cheaper in Mexico, with around 50 pesos (3.55 dlls) you can get a bag enough to last you a week.