I find that www.behindthename.com has the most conservative information on what is a "real" name as well as meanings/pronunciation. It does not include Elka, only Elke. I worked with a woman named Elke and she got Elkee a lot, but that was the only mispronunciation.
I just looked at the sight and found the name Elke too, which it says, is a form of "Elkanah" in Hebrew. I am almost surprised "Elka" isn't the shortened version. I also saw on the sight a user submitted name that spells it "Elka" and says that it is German, Croatian, English, Slovene. I have seen on other sights that it may be a Russian or Polish name...I am obviously trying to make myself feel better about this spelling. Thanks for the website.