May get flamed for this, but for those of you that are looking for a booster seat to fit into your 911, you may be interested in this. This booster has a narrow base to fit in the back buckets of your 911. (Check if it fits your car! Based on my research this one will fit a 991)
It’s on sale for $160 currently and if you stack the 20% coupon you can get it down to $133 before taxes. Free shipping too.
https://www.buybuybaby.