I just bought these 0,5 L plastic bottles with flip top applicator in my local paint shop. They are from Concept, a big British brand that apparently no Brit knows or talks about.
Interesting. I guess part of the problem is that we have very few UK professional detailers in Autopia, otherwise they might know of them. Doesn't look like there is any direct retailing, but now we know what to loook for, who knows? Useful link!