1.8" 128GB 256GB 512GB 1TB SSD for IBM Thinkpad X300 X301 T400S T410S | eBay
BEWARE: Lenovo Thinkpad L15 Gen3 SSD is practically un-upgradeable. Laptop comes with 256GB and bigger SSD is too thick to fit. There also goes a cooling plate on top. : r/thinkpad