Pretty much any place that specializes in exhaust work, not your local garage. Any real muffler/exhaust shop will have the equipment to bend and fabricate any pipe they need, the local garage usually will not have this equipment.
You make it sound sound like you just need one part…’‘an exhaust’’.
What is wrong with yours that you think you need …’‘an exhaust’’ ?
Define which parts are needed. Some available at parts houses like Auto zone, some dealer.
also try the catalogs the tuners use like Magnaflow.
I agree with the exhaust shop idea. We ( the Ford dealer ) will often use our local indy ( Tandy’s muffler shop ) if o.e. costs too much for the customer and for older and obsolete vehicles. We give them the option.