Just got this a couple weeks ago and it's been great. https://www.amazon.com/dp/B01KNWU66W/ref=cm_sw_r_cp_apa_glt_fabc_4H8S3T8KCQWTTD4GA4S7?_encoding=UTF8&psc=1 Nothing fancy but does exactly what you're looking for. The top just slides over the headrest and that's really it. Takes less than 10 seconds. Doesn't slide around at all when I'm driving, although my seats are cloth. It seems like it would work perfectly fine on leather though.
I have a couple of these. They are awesome and can be used even after swimming. No water gets through, they don't impact seatbelt use, and they are "installed" and removed in seconds. They just hang on the seat
Leader Accessories Black Waterproof Sweat Towel Car Front Seat Cover for Truck SUV Bucket Seat Dog & Kid Non-Slip Auto Protector https://smile.amazon.com/dp/B01KNWU66W/ref=cm_sw_r_apan_glt_fabc_505NJ78QE4ABQ3D3BGRK?_encoding=UTF8&psc=1
This is what I use post-workout:
https://www.amazon.com/gp/product/B01KNWU66W
It's basically a towel that has a pocket to slip over the headrest. The only complaint I have is if you tuck it tight to the seat it's just a little short and will expose a little of the front of the seat. If it were a couple of inches longer it would be perfect. But for my purposes, it works just fine.
I use these after a mountain bike ride, paddle adventure, or sweaty gym session.
A fan and one of these over the seat: Amazon seat cover towel
I bought some for after the beach/working out. Amazon has some that work well.
I researched the same thing for the ride home from the gym, very happy with this one:
https://www.amazon.com/Leader-Accessories-Waterproof-Sweat-Bucket/dp/B01KNWU66W
Leader Accessories Black... https://www.amazon.com/dp/B01KNWU66W?ref=ppx_pop_mob_ap_share
Leader Accessories Black Waterproof Sweat Towel Car Front Seat Cover for Truck SUV Bucket Seat Dog & Kid Non-Slip Auto Protector https://www.amazon.com/dp/B01KNWU66W/ref=cm_sw_r_cp_api_glt_fabc_TE1N4ZQJ9KR6R3JP5P23?_encoding=UTF8&psc=1
I have two of these for my sedan; it works great and appears to be good quality. It's a "towel" seat cover; it's got a pretty broad and wide form [so it should fit most, if not all standard seats]; is easy to "install" [literally, just put the cap on the headrest and drape the lower section over the seat], and it has a grippy inside that helps keep the cover from moving too much.
I have a waterproof backed seat towel that I got on Amazon that works great, it has a hood that goes over the head rest to keep it in place. https://www.amazon.com/dp/B01KNWU66W/ref=cm_sw_r_sms_apa_i_pHhAEbQDS2H90
Water bottle, a lock, headphones, booty bands, a sweet sweat belt, and a car seat towel.