I retrofitted the holding tank in our Bav36 (2002) 2 cabin version and used the standard Bavaria tank which I obtained from Clipper Marine. It looks a bit like the one in your photo. I did this because the boat is in Greece and I could be sure that it fitted. It was probably more expensive that going to another supplier but gave me some peace of mind that it would fit. Clipper marine were quite helpful.

Serendipity