Thanks for the comments guys. I'm still thinking about how I could reinforce this and detail it further. I can't use fiberglass and resin because I don't have space and I'm too young to use these kinds of materials. Any ideas? I thought I could use paper mache, but I've used it before and it only retains a certain amount of detail.
Here's the measurements, if other's want to use them. It's a pretty good size, not too far off from the actual size.
Length: 24 cm
Height (empty): 16.5 cm
Height (loaded): 19 cm
Width: 5 cm