What to do when the manufacturer stops making part that will enable you to pass emissions test ?
Aftermarket normally takes over…
RockAuto, O’Reilly, Napa, Advance auto parts etc etc etc…
If you give us more details about your vehicle, engine (4 different choices) and RWD/AWD and what part you are looking for, we might be able to help a little more…
Sometimes, if you catch the right counter person at the dealer and are nice, they can/will do a nation wide dealer search to see if any left in the country… Most dealers would be glad to sell off NOS (new old stock) parts to free up shelf space as well as stop having to inventory it…
DMP provides excellent advice above, especially his request to post which exact part(s) you need. Another source might be a used part, from a wrecked or junked 300. The wrecked car may not need to be the same model year as your 300. Parts recyclers seem to have access to databases which know which model years a particular used car part is compatible with, and will usually provide their customers that info gratis, if asked.
Donating the vehicle is also an option if it is near end of life.
If there is no aftermarket alternative part to a non-existent Chrysler part, the car must be scrapped.
Or you may have to sell it to someone in a state that does not require emissions inspections.
I presume you mean if the car needs that part in order to pass a gov’t required emissions test. Are used parts not allowed for emissions purposes?
It is my understanding that it is illegal to sell used catalytic convertors since there is no way to test them. Not sure that is universal.
And I suspect that is what the OP needs… Other parts, no issues, but if it is a commonly failed part, there is little likelihood of finding a used one that works.
All speculation since the OP did not explain.