I need a catalytic converter for my Impreza , I can’t seem to find one now . There are sone listed produced by BM but they have advised it’s not suitable any ideas where I can buy one please .

Last year there was availability

Why do you think the cat needs replacing?

Engine lights are on and has the following.

The error code is P0420 - catalyst system below threshold . 

The front and rear oxygen sensors are switching at the same time 

That code can have many causes - cat needing replacement is just one. Bad fuel, air leaks, bad earths, MAF/MAP, bad sensors etc. I would not change cat/s based solely on this evidence (P0420).

Thank you. What would you recommend as my next step please.