Lightest cylinder = faber (around 8~10kg lighter in weight but 8~10 thousand heavier on the wallet )
I got mine from CNG Kit Zone.. guys name Zeeshan (shani).. they have a lot of cars coming in for conversion.. decent rates...
i got it for 33.5k (landi renzo, orgig italian, (large EFi Kit, advancer, emulator, 55kg EKC cylinder)... Friends CNG is doing it for 41k (60kg cylinder) but MANY people are satisfied with it.. but ALTO will be cheaper.. i think around 30K max
(but i heard cylinders expensive ho gayay hain)..