I emailed info@teltonikadistributor.com, haven't had a reply yet, so carried on with my own research - this is what I found:
The part that comes with the Teltonika is from KEFA in China. It's very faint on the side, the full designation is KEFA KF2EDGKS-3.5. It is also made by Pheonix Contacts (the genuine item?). Their part number is 1790111. You will need to be careful to order or specify the right size because the part number is for a family of plugs which have different numbers of contacts. The Teltonika one is variously described as 3 way, 6 positions, 6 contacts and 3 positions with 2 levels. The Pheonix Contacts ones are available from RS Components in a box of 50 - bit expensive, and also from Mouser and Farnell.com ( not CPC Farnell) where you can get singles and price breaks at 10+.
Hope that helps.