Sloping cushion

I’m so pleased by the support on this site and how others help each other. 

I’m wondering if anyone had any suggestions for the type of padded, sloped cushions that they used to sell for car seats. They’re not available anymore. 

I’m currently not getting out , but use it on a sloping foldable chair in the kitchen. I need another one for a spare chair upstairs. I can’t seem to find any replacements online at all , I can’t be the only one who misses them. They were everywhere at one time