They are called HOB-BITS and are available at most good hobby stores. They have 2-56, 00-72, 00-80, and 00-90 hex head, fillester head, and flat head screws in various length. All my tanks have several varieties. Usual cost is about $2 for 5 of each flavor, nut bolt, and screw. I cleaned out my stores collection of hex and recessed bolts over time.

Yes I did steal your idea for the cleaning rods.