Turbo or non turbo (turbos you a round, V-band connection, non-turbos have a flange with bold connection)?
There is a guy on ebay parting out 3 perkins T6.354 engines. "ted-s-trucks", you can message him what you need or I can PM his phone number. He is familar with diesels but not marine specific parts so you need to really double check to ensure you are talking about the right parts as well as ensure the condition. Nice guy to deal with. He doesn't have the elbows in his pictures but I can see the exhaust "can" that connects the turbo to the elbow, there is probably at least one elbo in his stuff. If yours is not turbo, never mind.
There, I managed to answer it without telling you to contact TAD (ooops)