I spotted these on eBay – the sets were very affordable at £10 for 6 colours:
What’s cool about these is that they have tapered brush heads, meaning you use them for nail art – the odd dot here, the odd swirl – so easy to use too!
I believe this is a US brand, and it’s pretty cool because there isn’t anything like this in the UK. You can of course use normal polish with a thin brush, but this is an affordable way to get a nice collection of colours.
The seller on eBay is 1000_ideas.