It would be expensive to Buy just Clips for Fan...
What I would suggest is... To Get super glue and stick back your Current Fan Clip.... And even you can use Zipties to Tie down your Fan.... OR BETTER.. get a steady strong wire.. and make spring kind of clip for your fan....
Various Amazon sellers (in the US) offer the wire kind instead of the plastic kind, but as long as your heatsink has the same groove in the middle it should fit
Fan Buckle DGZZI 2PCS CPU Radiator Fan Hook Fixed Bracket Elastic Steel Fan Buckle 8cm Down Hook https://a.co/d/9s7aORS