Penumbra eZine is a professional rates paying publisher with multiple overlapping themed calls for submission:
[I]t is imperative that you include the issue theme in the subject line of your email. Submissions that do not include this information risk getting lost in our queue and not read before the deadline.
Their ‘Aliens’ theme is closing in a few days, but they are open to receiving Arthurian legend stories until the end of September:
What ho! (No, we don’t mean Guinevere.) For centuries, the magic and mystery of King Arthur and Camelot have enthralled readers. Thanks to great authors like Marion Zimmer Bradley and T.H. White, there’s a strong tradition of Arthurian books on the fantasy bookshelf. So add your own myths to the Round Table; send Lancelot out on one more quest. Let’s play in Camelot and Avalon until the mists gently cloak us from the modern world.
They’re after stories to 3,500 words and pay 5c/word, and will also consider poetry and reprints.
Check it out here: http://penumbraezine.blogspot.com.au/p/submissions.html