Saw on a Facebook group a guy fitted one of these. Said it cut the noise down considerably.
https://images.app.goo.gl/ZUnu9MBAN88HALa58
Was fitted on a Chinese heater.

Have you come across this https://planarheaters.com/product/a-4155-fuel-pump-th11-4-4ml-12v/

I think they exist but if you're using a Chinese heater these silent pumps cost about as much as the heater

Ok, so there are plenty of people out there discussing ways to make the traditional clicky fuel pumps quieter. It seems there must be a way to do a fan-style one which takes the same 12v input and produces the same fuel output, but without such a binary fuel pulse - again, a continuous fan-type thing comes to mind.

Has anybody come across such a thing? I'd love to buy it.

Non-clicking diesel heater fuel pump