How online ­jewelers are luring shoppers to their brands in reality:1. Pop-ups: Often standalone spaces—though they may be part of a larger retail event or installation—pop-ups, such as BaubleBar’s (above), offer insight into factors like how location affects foot traffic.2. Stores within a store: A retail experiment as old as the days of the department store makeup counter, co-branding with a large brick-and-mortar store gives jewelers ties to a venerable brand.3. Appointment-only showrooms: These spaces deliver a concierge-style experience, with a chance to interact one-on-one with sh