Portable didgeridoo
The construction of an inexpensive didgeridoo out of plastic pipe is well documented on various sites. In summary, all is needed is a 120cm long piece of 40mm waste pipe with a beeswax mouth-piece. This is quick to build and gives a surprisingly good sound with a pitch of around D2, the D two octaves below middle C .
This article describes how you can chop the pipe into sections that can be quickly reassembled into a working didg with no appreciable effect on its acoustic properties. The sections are small enough to be carried in a rucksack and can be reassembled in seconds.
All you will need is an extra few inches of the same pipe, a hacksaw, a piece of A4 paper, a pencil, a set-square, a file and some fine emery paper.