I found a pair of the Corteco accumulators for $60/each from USP Motorsports.
Took a few weeks to arrive but they are the right part and waaaaaaay better price than anywhere else I could find.

Mine were and have been bad for a long time, as long as I owned the car (10 years plus). Ride didn't seem that bad, only symptom was that it would sag when shut down.

It rides amazing now. Really big improvement.
Easy job, big results.

1985 300TD wagon