If anyone is interested in a travel router - small as a pack of cards, can be powered by USB, 3g dongle compatible - I recommend the tp-link mr3020/3040.

Do take care that it needs some configuring, because it has only one Ethernet port used as wan & LAN [1]

I had a slightly related question on how to set up a wireless-only setup for a startup. Hope someone has an answer to that - https://news.ycombinator.com/item?id=6800737

[1] http://www.lambdacurry.com/2013/05/configuring-the-tplink-mr...