What my sorority does is for initiation, the little makes the Big a paddle, and the Big makes the little a pillow. I think they usually just buy fabric and make the letters and the pillow from scratch, with the exception of a few girls that are severely sewing- challenged and buy premade pillows and just decorate them with puffy paint letters and what not (something definitely tells me that this semester when I get a little, I'll be in that second category

). If you wanted to buy a pillow, stores like
www.GreekGiftsEtc.com and
www.JoeToga.com will make either pillows or handpainted pillowcases custom made for locals. I think it's better to have Bigs make pillows though because it shows more time and effort that went into them.