Interesting. I think Amarim has it nailed with p/n 970755, which is also available through Volvo parts counters as well as the sources he mentioned. The dog ear on the connector is quite distinctive for the one in your picture, but isn't present in the connector I found, not that it would be critical if the other dimensions and bevelled shoulders matched. Heck, a couple of crimp terminal sleeves that fit over the male pins would work, protecting them and holding them in place with something like butyl caulk or hot melt glue.

The part I found p/n 9144275 was in a fairly detailed parts schematic that showed a wiring harness to the expansion tank on the right fender, with fitment including the 960 1994 production year, but it was a non-Volvo site. There may have been slightly different connectors used in different years or at different factories and of course your sensor is not original for your car.

I had initially checked Dave Barton's prancingmoose site with no luck. I now see the connector there has the vinyl protected terminals on the pigtail, which are not how they are shown in the schematics I found for 9144275, but are clearly correct for that particular connector housing that clamps shut.

Good luck getting it connected and working. A coolant level sensor is something I've always intended to add if I ever had nothing better to do, but there always seems something more pressing to do on my aging bricks. I'm now under the hood so often for other matters that it's now routine to quickly inspect the expansion tank level, giving it a quick wiggle just to be sure.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now