"Off the rack" is a common phrase used to describe clothing that is ready-made and available for purchase in stores. However, there are several synonyms that can be used to replace this phrase. One alternative could be "ready-to-wear" which also implies that the clothing is pre-made and ready for purchase. "Off the peg" is another option that is commonly used in British English. In addition, "off-the-shelf" is another synonym that can be used to describe clothing that is pre-made and available for purchase in stores. These alternatives can add variation to your vocabulary, making your writing or conversation more interesting and diverse.