FYI, You may not have to travel to Sri Lanka to try one.

You can get them e.g. in London UK: https://www.hopperslondon.com/

I've tried their Kings X restaurant, and while their food is delicious, and the decor is also really nice, its not particularly authentic, and I felt its a bit overpriced (tbf its an extremely central location). I don't live in London so can't suggest a better alternative, but I'm sure there are much more authentic restaurants.

> the decor is also really nice, its not particularly authentic, and I felt its a bit overpriced

That describes all of the restaurants in the Kings Cross newly built area. They are all different cuisines, but they all fit.

sadly, they don't open for breakfast.

I wonder if this is why I've missed them? I've lived within a few hundred metres of their Soho place for the best part of the last decade.