If you go down to somewhere that they sell pond plants, they might sell it there or sometimes it is floating around in the big ponds and containers they store their plants in so you could ask if you could grab a small handful and see what they say.
If not, ask around on this forum. I'm sure someone may be willing to ship you some if you can find a way to pay for postage.
You could ask one of your parents to use their credit card and purchase some from an online vendor (not AB).
If not and you have access to oak or indian almond leaves, you could use those. The tannins given off will diffuse some of the light and mimic the natural habitat of the neon tetras (where they come from it is mostly leaf litter, very dark water and little light).