This is my version of a common DIY probe design. The Carrier and Hub must be non-conductive (plastic), and the bearing balls and pins must be conductive (steel). The Body and Cap can be conductive, or not. The idea is that you wire the ball bearings together in the large spaces, and the pins complete the circuit. The Hub that the pins are pressed into is held in place via spring between the Cap and Hub. When the stylus is disturbed, the circuit is broken, signalling the CNC controller.

There are four 2.5mm holes in the body meant to be tapped for 3mm set screws. These screws allow adjusting the stylus to center. The fifth hole is for routing wires to CNC controller. The shaft on the cap is 1/2" for use with ER20 collet.

For the ball bearings, I'm using 5MM stainless steel bearings. https://smile.amazon.com/dp/B07HVLWPF6/?coliid=I1YLY8779T1TE8&colid=1P82YNQPGJUAV&psc=1&ref_=lv_ov_lig_dp_it

For the pins, I'm using 1/8" (3mm) diameter by 1/2" long stainless steel dowel pin. These will require you to grind a ball nose on one end. https://smile.amazon.com/dp/B00Z3VZDN0/?coliid=I105KP62XUIEFH&colid=1P82YNQPGJUAV&psc=1&ref_=lv_ov_lig_dp_it

For the spring, I'm using 15mm OD, 1.2mm wire diameter, 30mm long spring. https://smile.amazon.com/dp/B07883QTSN/?coliid=I4KEJTGRU68KX&colid=1P82YNQPGJUAV&psc=1&ref_=lv_ov_lig_dp_it

For the Stylus, I'm using a Chinesium Renishaw A-5003-4797. https://smile.amazon.com/dp/B07G8DWBYF/?coliid=I372WOAA7OJN01&colid=1P82YNQPGJUAV&psc=1&ref_=lv_ov_lig_dp_it

This is currently proof of concept while I wait on parts. Since this may require some adjustment, I included the Fusion file.