JCPenney offers the Royal Velvet Carmen Blackout Grommet-Top 50" x 63" Curtain Panel in six colors (Evening Sage pictured) for $35.99. Coupon code "AFFSHOP1" cuts it to $30.59. Opt for in-store pickup to dodge the $8.95 shipping charge. That's $29 off list and the lowest total price we could find, although we saw it for $8 less in April. This room-darkening curtain is made of polyester.
Note that it's also available four larger sizes for higher prices.