Question about springs for disc/canti lever brakes

[bagpuss]

Gents.
I am repairing a much bashed Carrera Gryphon for a mate .
The internal spring for one of the Tektro Lyra mechanical disc calipers is missing/broken.
It fits behind the piston .
I cannot find any replacement ones listed on line?
Are they the same size spring as used in many canti lever brake caliper arms ?

Thanks in advance.

Paul.