You can obtain the ESXi installer software either from an OEM or from the Broadcom Support Portal.
Register on the Broadcom Support Portal. For more information, see Register for an account on the Broadcom Support Portal and Communities.
For product download instructions, see Download Broadcom products and software.
For download of offline bundle ZIP files for ESXi patches and updates, see Downloading Broadcom PTF files and solutions.
For more information, see VMware to Broadcom Support Frequently Asked Questions.