Well these aren't people shaped, but i bought a custom tank from
https://www.spunaluminumgastanks.com/
for my bird, and they welded bungs right where I asked them to. Very high quality work. Don't have to worry about gas compatibility or uv breaking down the plastic and i bet they're far more resiliant in a crash than most other options. Ie not going to burst open and shower you with fuel. Might see if they can weld some plates on them that allow for securing with a seat belt.