Brocken chronograph button

Hi all, I own a 1993 tag Heuer formula 1 chronograph ref CA1210-R0 with an ETA 251.264 movement. it has been sitting in a drawer for some time, I have realised that one of the chronograph pushers has fallen off (the main part of the pusher is still there but the cap and spring are gone) Can anyone inform me where to purchase a replacement, preferably no original as I have a tight budget, and will like to fix it as cheap as possible. and it is also missing a battery clamp.

Another issue is that it loses a lot of time and runs incredibly slow, is it just because it needs a service? or is it because of the fact there is not battery clamp?

Assuming you've changed the battery it probably needs servicing. Even though it's a quartz movement there are still moving parts that wear and the oil gets claggy.

do you know roughly how much a service will cost?

If you take it to a local watchmaker £200-300
If you send it to TAG Heuer probably £300-400

OK, do you have any idea what size chronograph button I will need and where to get it from? I know Cousins UK have some but I don't know which one would fit.

Sorry, I don't have any idea.

Thank you.