I had the same issue where the original strut failed on my A54. I contacted Amel in La Rochelle and initially they indicated they did not have a replacement. However, upon sending them a photo of the label on the side of the strut (very hard to read), they were able to provide a replacement.
The only issue I have with the new one is that it is too powerful and often opens the lid too fast and with too much force. In fact, I had Amel in Martinique install a restraining strap to prevent the screws from popping out - which they did twice after installing the new one.
I believe the strut I got is the wrong part, so I welcome anyone actually finding the correct unit. I tried many other sources as well, but no luck.
By the way, I have the earlier full-size lid type. I would imagine those with the reduced size lid will have even more problems with excessive up stroke.
Phantom, A54 #44