If you are regularly around children of a certain age, then you will no doubt find yourself playing with their toys. When my children developed an interest in dinosaurs, inevitably, I bought them some plastic / rubber models. Some of the models came with their own jungle scenery bits, as pictured below.
Although these bits are very cheap and plastic looking, some of them have excellent potential as wargaming terrain in their own rights. The smaller plants in the picture (i.e. not the palm frond things) look good enough in real life to represent a field, or other dense foliage region. When my children tire of these toys (or they get so broken as to be unplayable - more likely!), then some of these bits will be finding their way to my modelling table. For the smaller bits, planting them on an MDF board and adding some lichen / moss plus scatterings will certainly make for a good section of dangerous or difficult terrain. Perhaps even mysterious terrain if I paint it in a certain manner.
So, the moral of this tale is to keep your eyes open. There are alternative bits for scenery and terrain out there beyond Citadel Miniatures and the Model Train and Railways Hobby. Even dinosaurs need their jungles!