NEW YORK — Toys R Us and Bon-Ton may be gone but they haven’t been forgotten.

Companies like Target and online mattress company Casper are creating playbooks to pick up market share that those and other defunct or dying retailers left behind.

Casper, for instance, is teaming up with department stores like Nordstrom to introduce pop-up mattress shops in areas where Mattress Firm, which filed for Chapter 11 bankruptcy in October, had locations. And Kohl’s has been mapping out where retailers like Bon-Ton and Sears shuttered stores so it can target those customers with specific ads.

Kohl’s is also adding more beauty products, which had been an area of expertise for Bon-Ton, the York, Pennsylvania-based department store chain that closed the last of its stores in August.  Kohl’s believes one-third of its store base is benefiting from department store closings, up from one quarter a year ago.

Target CEO Brian Cornell estimated up to $100 billion in market share that’s now up for grabs — about double what he foresaw just a year ago. In response, the company is accelerating its store remodels in areas where bankrupt retailers once had stores. Target has devoted extra space at 500 of its stores for bigger toys like electric cars, playhouses and musical instruments as well as adding nearly 200 more products. About half of those locations are about five miles from former Toys R Us stores.