I originally bought a cheap CAP curl bar but ended up returning it because the thing felt like crap, squeaked like crazy, and I just hated using it. Ended up getting an Xmark curl bar and it was just way way better.
Still on Amazon for around $100:
XMark IRONHORSE Olympic Bar Super EZ Curl Bar Olympic Curl Weight Barbell, Compatible with 2" Olympic Weights or 2" Bumper Plates, Great for Bicep and Tricep Muscle Isolation https://www.amazon.com/dp/B07Z9PKJ8Q/ref=cm_sw_r_cp_api_i_NxP3EbHPQDAVR
There are also other xmark curl bars on Amazon for cheaper from my time using it Xmark seems to be pretty legit and I’ve read other posters stating the same.
https://www.amazon.com/dp/B07Z9PR854/ref=cm_sw_r_cp_awdb_t1_tzP3EbTMWW4H2