I have a Jinhao pen as well

https://www.reddit.com/r/pens/comments/qwhyd3/npd\_jinhao\_rollerball\_a\_little\_extra/?utm\_source=share&utm\_medium=web2x&context=3

and it used the same screw in refill as what yours likely does (5th pic):
https://www.amazon.com/Gullor-Culture-Jinhao-Rollerball-Pattern/dp/B00CHXK7WY?th=1

Great pen, quite remarkable for the $20 I spent on it, but the refill is not good. This is a common trait on high end pens as well, including Montblanc's.

I used needle files to widen the inside of the nose piece to accept gel refills like Pentel Energel, Uni-ball Signo. (like this: https://www.amazon.com/Hardened-Strength-Barrette-Crossing-Equaling/dp/B07PPYWSCY)