Quote Originally Posted by BlackMage
Quote Originally Posted by Indra
"just a sec"
сию секунду(???)
одну секундочку. My teacher says, дну скундочку.
Yes, it's the most polite answer

You should know that all of the mentioned phrases:
в два счёта
сию секунду
одну секундочку
are used in a different sense, i. e. they are not synonyms