One can make very nice needle point probes from sewing needles (ideally gold flashed which for some reason embroiderers like, but for us, makes them solderable) mounted in Bic Cristal biros. Remove the ink tube, push the brass part of the tip out of the plastic part, and punch the little ball out of the brass part using a pin or similar from the inside. Wash out with IPA. You can then solder the needle into the brass part, with the length you want protruding, solder a test lead to the eye and reassemble the Bic with the lead exiting through a hole in the plastic plug. The only major disadvantage is that the barrels are polystyrene, which is rather brittle in its clear form.
I wonder if one could build a logic probe circuit with tristate LED indicators small enough to fit inside the barrel of a Bic?