Nothing at all against Ansa, but I am pretty certain the oem was Eberspaecher.
Mine was already 2 piece like your '88.
A local welding shop may be able to adapt the 2 pieces together for you for not a lot of money. I have done similar adaptations on some BMWs, and it is really no big deal. Perhaps design the 'adaptor' section so that it is is welded to the center section, but clamped to the rear section, so that when the center finally goes, you can easily replace it.
'Specialty' exhaust shops tend towards full replacement, and are weld-averse. Their own crap parts are so short-lived, that repairs or partial replace is not usually worthwhile.
Oem quality German exhaust bits are heavy gauge, expensive, and can last 10+ years (as yours did), so repairs/partial replacement can often be justified.
1986 300E 5-Speed 240k mi.