Only Apple and OWC make compatible sticks for your machine. Here's the ones OWC puts out, the 1 TB is the largest: https://eshop.macsales.com/upgrades/macbook-pro-retina-15-inch-mid-2015-2.8-ghz-haswell-crystalwell/internal-drives
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One option is to go with a Flash storage device, then form a Fusion drive:
Only Apple and OWC make compatible sticks for your machine. Here's the ones OWC puts out, the 1 TB is the largest: https://eshop.macsales.com/upgrades/macbook-pro-retina-15-inch-mid-2015-2.8-ghz-haswell-crystalwell/internal-drives