I’ve recently been working on a small HF amplifier project, using common TO-92 style transistors. I needed some heatsinking capability to keep the transistors at a reasonable temperature, so I whipped a couple small aluminum heatsinks up on the lathe.
They’re really simple, starting with some ~1/2″ round bar, drilled out the middle, parted off the section, then drilled and tapped the set screw hole.
They’ve got a really good loose contact fit with a TO-92, and a little bit of thermal paste goes a long way in making them as effective as possible.