An alternative exists: simply buying ready-made instant yerba mate. It looks like this:

As you can probably see, it's a fine powder, a teaspoon's worth is about equivalent to a fresh gourd fill - so, it's quite efficient for when you're on the go.

Do note that:

• the powder is indeed fine and very sticky, so you have to take care when preparing your brew (e.g. when backpacking, shield yourself from the wind). Otherwise, it might get everywhere.
• the taste is somewhat different from "real" yerba mate (I would say not as good, but passable).
• the powdered form contains a quite substantial amount of caffeine per teaspoon (about comparable to a typical energy drink can). While nearly not as dangerous as pure, powdered caffeine, you should still be mindful of the dosage.

As a bonus, after you're done backpacking, a small amount blends surprisingly well with vodka (but recall the caffeine dosage note above)!