Some time ago I made a 1/25th scale three-section radio antenna (that actually slides) out of steel hypodermic tubing and a straight pin (photo below). A company now makes a product that eliminates the step of finding affordable tiny tubing that has compatible inner and outer diameters. Albion Alloys makes packs of what they call Slide Fit Tubing that has multiple sizes of nesting tubes. The packs contain four different sizes of tubes about a foot long. I bought one at Hobby Depot for $6.80 last week. Hobby Depot had a few different sizes. They come in a bunch more in brass, aluminum, and nickel silver.
Here is the URL for Albion with a picture of one of the packs: