I have the “zero degree knee” off of amazon but there are cheaper ones if you just search via those terms. Like ~20 bucks. Super easy, works well, and I’ll probably donate it after (lightweight enough to ship).
I’d check it out!
Zero Degree Knee Pillow - Post Surgery Knee Pillows - Knee Foam Wedge - Knee Rest - https://www.amazon.com/dp/B07G4KX7G2/ref=cm_sw_r_cp_api_i_cnVmEbYDRTXE7