A few practical travel options came up:

• Use multiple SD cards and rotate them daily. This is the simplest and lightest approach. It limits losses if a card is lost or corrupted, but it is still only a single copy.
• Back up to a phone or tablet with an OTG/card-reader setup. This is a lightweight, low-cost option if you already travel with a phone or tablet. For more safety, copy again from the phone/tablet to a USB flash drive so you have two copies before reusing a card.
• Use a dedicated backup device with an SD slot. A portable SSD backup device can copy cards without a computer and may be the most convenient standalone option, though it adds cost and another device to carry.

For best protection while traveling, keep the originals and backups in different places. In general, the safest lightweight workflow is: shoot on multiple cards, back up each day to a second device, and don’t keep both copies together.