I'm using these fans: https://www.aliexpress.us/item/3256806843870946.html

Configured as PWM fans in Klipper as bed fans. This is a little bracket intended to hold them in place. It's for a 350mm printer, but the model is sorta parameterized andyou can tweak it if you want.

The airflow path is a tad mediocre and I intend to redesign this sometime soon to include a baffle. For now, I used Kapton tape. Bad, but it proves that the concept is viable. 

These are much more effective than The Filter fans at heating up my chamber, since they're massive power hogs (12w each, according to their stickers). If you add enough fans, you will definitely outrun your bed. One at 100% power may be enough to outrun your bed. Don't run them at 100% power.