I put together some thin thermistors as a proof of concept. Aiming to get under 1/16" thick. Very few long lead thermistors on digikey are under this mark.
I ordered some flat flex cable with connectors, Digikey offers inch increments between 2" and 8" and a variety of termination options, all as value add parts. The flat conductors inside are 0.05" wide on 0.1" pitch.
Digikey stocks 10k NTC thermistors all the way down to 0201 SMD package, but I went 0805 for two reasons. First, they're the same thickness as 0603 chips, but in an easier to handle and more robust package due to the larger area for solder to stick to. Second, 0402 and smaller won't reach across the space between conductors. The manufacturer of this wire makes it in 0.05" pitch as well, but the 2 conductor version isn't stocked at digikey.
0805 NTC thermistor and flat flex cable