Dial test indicators are similar to dial indicators, but are typically more precise and have a smaller range of movement. Rather than a plunger that moves in and out, they have a small lever arm with a ball-shaped tip that moves up and down. This enables the tip to be inserted into a small hole so that the hole can be precisely centered on the lathe axis - an operation that could not be done with a dial indicator. Check the typical import tool catatlogs (especially the sale flyers) and you should be able to find these from under $30.