Good call, you'll never regret having a poncho kicking around. I'd say GoLite. Find a coupon code (on lots of sites right now) and you'd have around $40 into it. Looks like a nicer tarp than the S2S too, and lighter of course.
I doubt you could get the cuben, tape, webbing, shipping, etc. for much less than $50. If you did, you could look forward to replacing it soon enough. Methinks MYOG won't save you any money for an item like this either. Best of luck!