I second purple! I have the simply seat cushion and use it on harder chairs and in the car.

I also recommend the original Mckenzie lumbar roll. I use these 2 together for driving and it helps a lot.

Edit: forgot the footrest! I use this one but there are a million just like it in Amazon. It is simple but does the job https://www.amazon.com/dp/B07QHBS21X/ref=cm_sw_r_cp_apa_glt_fabc_PDQYD2Z7EE0ZTATMG3F2?_encoding=UTF8&psc=1