To get medical supplement from AARP you must be a member. My wife’s Plan F from Blue Cross is pretty cheap.
I have been a member of AARP since before 1989 - $16 a year. I had the cash money insurance policy if you were in the hospital and my husband had cancer and was in the hospital a lot and I got a check for $10,000 from that policy through AARP and another one over $2,000, no questions asked. Just sent the hospital bill in and the check was sent. I had double cataract surgery in 2012, two day surgeries and that policy sent money for those two times. That policy has nothing to do with Medicare or any hospital/doctor insurance, it is just cash when you are in the hospital.
I have plan F but for me since I am 80, the price was much higher than the UnitedHealcare one through AARP and the price has not gone up as I have aged. Outside of AARP, the price keeps going up the older you get.