Magnifying mirrors of 30x or higher tend to be small enough to refer to as magnifying glasses, intended for use by jewelers in their close examinations of stones. Mirrors for cosmetic or decorative purposes tend to top out at 20x magnification, with 3 to 6x magnification being far more common.
Typically, 30x magnifying glasses are relatively inexpensive, with many costing less than $5, as of August 2015. They are available from specialty retailers such as AliExpress.com or through massive online retailers such as Amazon.com or eBay. The same sellers offer cosmetic mirrors in a range of colors, styles and magnification levels, as well. Since eBay is an auction site that derives inventory from users rather than a traditional retailer, there is no guarantee a particular product is in stock on a given day.