Anyone got a good infuser for tea when out traveling and camping?
No, I have a strainer that probably cost a quid from Wilco's. Unlike coffee you're not going to improve it by infusing it in some different way, best thing to do is give the tea space, constricting it in some fancy gadget hinders that.
You could go for a pair of nestling cups with a strainer packed inside, brew in one (Preferably with a lid) strain to the other. But if they're a tea lover, what are they using now? They've probably worked out how to achieve what they're looking for and may prefer to receive some really nice tea.