there are plenty that will fit (google it) but they are not approved, or "fit properly" except for the porsche dedicated ones from the OPC
we had murders trying to get a good fit, and did indeed settle for a britax from halfords, because it was the smallest/slimmest,
however not the safest or best quality, it really is hard as lets be honest, a 911 is not a family car, i use the britax only when i must, and take extra care with my cargo.
also its prudent to remove the velcro seat bottom for a better fit, due to the shape of the 911 seat bottom.
as far as strollers go....good luck with that, if you have a 2 wheel drive, you might be able to find a collapsable one, but we couldnt, if you have a 4 wheel drive, then no way at all.
it will have to lay across the rear footwell, or you could do as we did, and buy a cayenne GTS also. (lol)