Any suggestions where to get a cheaper catalytic for '98 mitsubishi montero?

Question

I have p0421 code on my 98 mits montero and i think need to replace it. Where can i get a cheaper one? i live in california,usa.

Answer 1

P0421 Warm up catalyst efficiency below threshold (Bank 1 California)

This is for the right bank side for the catalytic convertor, You need to be sure,  you replace the catalytic and where not sure you would have the same code set,  What can set a P0421 as a catalytic code would be its downstream 02 sensor  or the catalytic monitor sensor, rather than the catalytic