Need to find a compatible catalytic converter for an older VW T5 3.2 (2006-2009) when OEM parts are discontinued, and understand aftermarket quality, cross-brand compatibility, and check engine light

Need to find a compatible catalytic converter for an older VW T5 3.2 (2006-2009) when OEM parts are discontinued, and understand aftermarket quality, cross-brand compatibility, and check engine light implications.