I would piece fabric if I loved it and wanted it in the quilt. I would try to make the seam as transparent as possible (ie: line up and sew using the "repeat" if it is a print). Since you have such a small amount in a fat quarter this might not be possible. Antique quilts quite often have fabrics that are stitched together to make a large enough piece of fabric. Good luck and let us know what you decide to do.