Is there any shop(not online shopping) that I can buy a Light Novel?
Hmmm, no bloody idea. But, i think you should try your luck at Red Dot Geek. If not, Browsing bookstores could be your best chance. It is a bit time consuming though. However, if you are looking for a specific title then I think your chances maybe even slimmer.
I don’t think Reddot Geek has any Light Novels.
As I recall, Vijitha Yapa had some manga, but not sure about Light Novels. I’ll ask around and see if anyone knows anyplace that sells 'em.