I've seen This fan (ldo DF5015H05S) mentioned as a replacement, 4.4 cfm @5000 rpm, supposedly faster than the stock fan. Found a Post on the prusa forum also suggesting good results from a fystec fan, this links to an aliexpress page but have seen on eBay and Amazon.

First link is to kb-3d which I've have good experience with in the past for some mods.

Edit: I did swap my mk3s+ to an skr mini before modding the heck out of it, that is an option if you're willing to put some time in and aren't concerned with keeping totally stock. That'll let you use 12v and 24v fans too which open up a lot of options, but it will see you having to recrimp some connectors so not super straightforward to flip back and you'll lose the prusa specific cuatomizations. I tried to recreate some as klipper macros and had found a repo outlining the same, I'll see if I can find the last config I used (current machine is a Frankenstein, different board and setup entirely) just so it's available if anyone else wants it.