Skewers, chopsticks or fine dowelling rod (which is cheap considering how little you need).
Fencing wire or cyclone mesh grade are also a very simple solution together with a little modelling putty work for the inlets.
The big ticket item is the actual "U" gutter. You can do that with wine bottle lead (if you can find any these days) or any reasonably thick tin-foil. Form it with a chopstick by just folding it.
But it's still a nice piece.