If you have a knife, a collection of thin bamboo sticks originally meant to be home decor, and an idle mind, you can make your own bamboo pen.
Carve diagonally into the tip of the bamboo (if you didn’t pick yours up from a home store, but from your backyard, you’ll have to dry it in the sun first for a couple of days). Go in at a 45º angle first. Then carve the finer details in so that you end up with a teardrop shape.
The bamboo absorbs some of the ink, of course, but the hollowed-out area can hold a tiny pool.
All the doodles on this Moleskine sketchbook page came out of a single bamboo pen, Waterman Florida Blue and Noodler’s Singapore Sepia.