CO2 Tank - $50
Dunno if this is the same or similar to Powertanks, but maybe a basis for DIY version? It's supposedly filled, too.
'91 Toyota Pickup
'09 Kawasaki KLR650
'12 Gunnar Rockhound 29
"They say the test of literary power is whether a man can write an inscription. I say, 'Can he name a kitten?'" -- Samuel Butler