When I worked in Saskatoon the company I worked for used the exact same black plastic "probe holders" as cable glands which is what they are actually used for. The strain relief type have a pigtail extension to prevent the cable from breaking at the seal.
Anyways we ordered them from
B&E electronics for around 50cents a piece and they come in a bunch of sizes. So $10 for something worth 50cents and relabeled as a probe holder is quite the rip off.