Do a search for bubble lenses as well.... Cutting a strip wide enough for the eyes, try and find something stiff that'll match the curvature of inside the bucket, tape the two together. Warm up your oven, I think the temp was 250 F, put the taped lens material in there, let sit for three to five minutes, keep checking every three, as you don't want the lenses to melt. Also put the assembly on a cookie sheet covered with tin foil in case. As you may guess, the lenses must be taped to something that can withstand heat of 250 F so cardboard is a no go.
I can't find the hero lens thread... Maybe it's too old. The guy made his own bubble lenses in the oven, I was trying to find what temp... Maybe try 150 F first, it may take longer to do the curve your looking for, but at least it won't melt the plastic to bits. If it's thick plastic, you may need higher temp...