Maybe an idea...
I have used older lines, fat quarter bundles, to make quilts but then needed yardage to make sashings, border and backing. I had good luck with finding yardage from newer lines by the same manufacturer as they might still use similar colors, so Andover in your case, or taking the top into quilt shops and buying tone on tone by matching it to go with it. The latter works well for backing fabric as it is not directly next to the front fabric when the quilt is in use.