I don't like piecing backs, either - I only do it if the perfect fabric isn't available in wide widths.
I buy almost all of my quilt backings from "judipat47" on eBay - she's got over 100 different prints and solids in 108" wide fabrics, plus some more in 90" wide and 120" wide.
The price is only
$7-10/yd and the most you pay for shipping on any order is $10.70. She's always super fast and friendly and the quality of the fabric has always been very good.
http://stores.ebay.com/QUILT-UNIQUE-FABRICS-AND-GIFTS
She's got several purples in marble, solid and tone on tone.