I was looking for exactly the same thing just last week - in the end I settled for 3mm MDF available in large sheets from Wickes. That's what I used for basing those tube sections in your Necromunda game.
The 2mm stuff is often available from art material suppliers for use as backing board.
The 2mm stuff is often available from art material suppliers for use as backing board.
Figures painted in 2016: 4 
"What this game needs is a panda with a chaingun."
"What this game needs is a panda with a chaingun."