Hi,
Signed up specifically to reply to you - as I have similar issue and found your post via google....
So I have a Kinetic Plus B (443028), from some 12 years ago.
The actuator is 100331.27K T105
I have managed to break the "teet" off the end that engages to the summer bypass mechanism.
So looking around:
£50ish:
https://electricspares.co.uk/product/vent-axia-actuator-kinet-airminer/
But how about this:
£14: Got to worth a punt?
https://www.leisure-parts.co.uk/thermoactuator-eltek-b10-kt105/product.pl?pid=10656
UK seller of Eltek
https://www.radward.co.uk/eltek/10033127k
Aus Ebay - but used in other products, which might help. This has the same "teet" as mine did....
https://www.ebay.co.uk/itm/143189739579
But I haven't worked out all the product coding as (all these - at the "right sort of price", have different ends):
https://www.ebay.co.uk/itm/405603465584
https://www.ebay.co.uk/itm/356691708759
https://www.ebay.co.uk/itm/205336941517
Hope this helps.
Let me know where and what you do.
Thanks, Ade