I have that type. The penetrator is easily replacable, and the cost isn't high. You will see them for $110, but the $15 import ones work fine. Test blocks are also readily available from places like eBay. You can also make your own by HTing four 2" squares of 1/4" 1084. Leave on as-quenched, and temper the other three at 300, 400, 450. Have them tested by someone with a good tester. Once you know their exact hardness, write it on them and use them for checking and calibration.
What is absolutely important is that the tester has the full set of weights.
I have a bunch of the testing tables ( what you place the blade being tested on), so if you need something like that, I can help you out.
It weighs less than 100 pounds, and will easily fit in a car trunk. A good stand for it, if you don't have the spare bench space, is a rolling welder cart. It fits just right on the top. Acessories and test blocks can store on the shelf under it. Put a grill cover ( the one that fits the smal egg cooker) over the unit when not in use to keep it clean.
What is the price being asked? Post photos of the tester and what comes with it if you can.