Problem with belt length in S80 (with pictures)

Since in the foreseeable future young people will be waiting with us, I have a few days ago the baby bowl and the pram from our 2 year old son out to see if the things fit in the S80. Our son is now sitting in a “normal” child seat which also fits very well in the S80. The pram would also fit in the trunk, even if it is then full. The problem is the Roman baby bowl: The straps on the back bench are about 20cm too short!!! n seat is not normally strapped or only frayed with a lot. But then the shell “turns” back over through the too short belt. At Volvo I only saw a kind of buckle as a belt extension – but that won’t be enough of the length. Otherwise there are no alternatives from Volvo to my dealer either. We were already out and tried out baby shells from other manufacturers, but the straps at the back are simply too short. Do you know any advice what to do?? – I’m so baffled…