I have what appears to be the same Buck Booster unit. I took the the brute force approach and added extra heatsinks taken from a dead Asus motherboard to spread out the heat. I removed the noisy little stock fan and replaced it with an extra quiet 120mm Arctic F12 PC case fan
I used thermal epoxy to attach the extra heat sinks. My booster is wall mounted so the the top and bottom are clear to allow room for these additional heat sinks and the 120mm fan. The little stock fan is replaced with an ABS plate but its hard to see in the photos. The plate is held in by the stock fan's extra long screws that go into threaded holes of the stock heat sink. The 120mm fan's hub is then attached to that plastic plate using 3M double sided tape. Then I added hot glue on the long brass standoffs where they contact the 120mm fan's casing. Not pretty but it securely holds the 120mm fan in place. I hope you kept the optional long brass stand offs they gave you!
The thermal conductivity to the additional two Asus heatsinks is good and they're just the right size to fit within the large 120mm fan's air flow. The 120mm fan is barely audible even when the buck booster has it going at maximum speed. It only goes on briefly for 15 seconds or so even when I've maxed out this unit's 1500W to charge my 18s LIPO e-bike. Actually, I wish the 120mm fan would be activated more. The fan is so quiet it could be on all the time without me noticing much.
I'm in process of modifying all my charging equipment to use quiet 120mm fans. The stock little high speed fans are very annoying in my quiet garage environment where I'm also doing other stuff.