You can check out my list of brands and styles and look for brands that I marked "BDSM" or "dominant" or "submissive" (depending on her favorite vibe).

You can also spruce up any vanilla lingerie set by adding a custom collar-and-cuffs-and-ankles set from collarfactory. You'll measure her wrists and ankles and neck, and it'll be exactly the size you need. Then pick up some carabiners and panic snaps and some lightweight chains and stuff. (Later, you can take off all of the vanilla lingerie, and just the collar & cuffs still count as BDSM lingerie!)

You can also get a cheap AVIDLOVE skirt in whatever color you like, thigh-highs from Trasparenze or socks from Sock Dreams, and a tight white t-shirt or crop tee. Add cuffs and a collar, and a "schoolgirl" or "cheerleader" look turns into a "good girl"/"bad girl" outfit.