In the past, there have been questions about how to back-up SD cards to a HDD without bringing a laptop on a trip. There is an Amazon sale on a RAVPower FileHub Plus. Normally $49.99 on sale for $30 with code YVZT6QGO. I saw this on Kinja Deals and you may need to go to Amazon from that site for the discount code to work.
http://deals.kinja.com/this-30-gadget-is-actually-three-devices-in-one-1746727424)
It creates a WiFi network of up to 5 devices and has an SD slot , USB port, RJ45 Ethernet port and a built in 6000 mAh 5V back up battery. You will also need a smart phone or tablet to control the connections.
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