Yes you can buy these locks but beware: they come in many different sizes so you will need to measure yours first.
Remove the "Euro" lock from the door by removing the screw holding it in place on the side of the door. Turn the key one way then the other and pull/push the lock at the same time until it slides out.
Measure from one end to the centre of the fixing screw hole then from the other end to the centre of the screw hole. Measure this in millimetres. This will give you the size required eg 35/45
The part should cost no more than £15 really.
You will be able to find one on google by typing in "upvc euro door lock" or something similar.