Both tolino and Kobo will do it. The attached screenshots are taken using my tolino epos and my Kobo Glo. The two screenshots for the Kobo are of epub and kepub. The first is your book unchanged and uses the Adobe RMSDK. The tolino will be using this as well, but, I don't know if they use the same version.
Kepub is Kobo's own format. It is basically an epub but Kobo has their own renderer which is based on what was once called ACCESS, but, whose current name completely escapes me. There are plugins for calibre to support the format so it is no harder to use than any other format.
In each case, the font choice on the device is "Publisher default" which means to use the built-in fonts. I fiddled a little with the size, margins and line spacing, but, mainly because I had set these on the Glo to something ridiculous the last time I was testing something.
The filenames should tell you which is which, but:
- tolino-epos-test-sinhala.png - tolino epos - epub
- kobo-epub-test-sinhala.png - Kobo Glo - epub
- kobo-kepub-test-sinhala.png - Kobo Glo - kepub