Supply house spares for supermarket own-brand tat is very limited - that's one of the reasons it's cheap.
https://www.espares.co.uk/search/mo2219853/lawnmowers/powerbase/m1g-zp3-300c1
Your best bet is to determine the part number off the switch itself and see if you can get something like it off eBay or Amazon etc.
Sdjdj, June 2022
