Waltz has traced it back to Valentin E. Löscher in 1718, but -- with some help from Eberhard Jüngel (link) -- I have traced it back a bit further to my own favorite Theologian, Francis Turretin, who stated, in his Institutes of Elenctic Theology at Tomus II, Locus 16, Question 1, Section 1:
"Luthero dicitur Articulas stantis et cadentis Ecclesiœ"
You can see for yourself:
I don't have access, at the moment, to a first edition of Turretin's Institutes to verify that the quotation appeared in the original edition. Both Waltz and Jüngel (linked above) provide some interesting bases for the pseudo-quotation or paraphrase. Jüngel notes that previous attempts to definitively track down the quotations origin have proved fruitless.
On the other hand, the Smalcald Articles do suggest that Luther viewed the issue as being a stand-or-fall principle, and so do many other of Luther's writings. The Smalcald Articles provide a good basis for the quotation as a paraphrase when they state:
5] Of this article nothing can be yielded or surrendered [nor can anything be granted or permitted contrary to the same], even though heaven and earth, and whatever will not abide, should sink to ruin. For there is none other name under heaven, given among men whereby we must be saved, says Peter, Acts 4:12. And with His stripes we are healed, Is. 53:5. And upon this article all things depend which we teach and practice in opposition to the Pope, the devil, and the [whole] world. Therefore, we must be sure concerning this doctrine, and not doubt; for otherwise all is lost, and the Pope and devil and all things gain the victory and suit over us.(source)
P.S. Luthero dicitur means "It was said by Luther."
P.P.S. See p. 633 of Volume 2 of Turretin's Institutes in the Giger-Dennison edition, if you wish to see how Giger-Dennison handled this.