The safest, most reliable source for firmware is always the manufacturer. However, Huawei does not make firmware for its carrier-grade ONT devices publicly available for direct download by end users through a simple web search. This is a deliberate security measure.
The upgrade may have wiped your ISP configuration (VLAN IDs, PPPoE username/password). Log back into the web GUI, go to the WAN configuration page, and input your ISP details, or restore your configuration backup file. huawei echolife eg8141a5 firmware download free portable
While the firmware itself isn't "portable" in the traditional sense, you can create a portable toolkit on a USB drive to manage your router. The safest, most reliable source for firmware is