I have a bit of advice on both pre-cured gourds and yerba mate bags. Pre-cured gourds, it seems, can be purchased at http://www.mymateworld.com. I have not personally purchased anything from there, just discovered the gourds while browsing. There are some fairly cheap pre-cured gourds as well, and instructions on using them.
As for yerba mate 'tea'bags, I would recommend Guayaki brand bags as they are likely the most accessible--your local grocery store probably carries them (I know, for instance, that King Soopers does), doing away with the rather expensive shipping and handling charge incurred from purchasing them online. I assume that by 'advice on yerba bags' you meant advice on obtaining them (?) If not, disregard this paragraph. If you would prefer a different/higher quality brand than Guayaki, shop around online. There are plenty of places with such products around.