Greetings!
The best PBT backlit compatible keycaps I have ever used is the Vortex PBT+POM Doubleshot Keycaps. I used to get it from Amazon, but it is not available there anymore.
Checked mechanicalkeyboards.com as well, and they ran out of stock as well (although they have a vast selection of keycaps, among other stuff). Referring to your location in
Australia, I gave MechKB Australia a look, and it seems that they do not have that as well. Keep looking around for them. They are available in black or white, and both are in
OEM profile, which should be great for your Varmilo.
Cheers! Sorry I could not help much but at least I can give you a recommendation.