gas shotgun leaking like a sieve

[Fat-jd]

trying to get hold of seal for a acm m500 gas shotgun its a clone of the tm, looked everywhere has anyone had any experience trying to stop obe of tgese leaking thinking of slinging it in the bin but when it works it's really good fun any help on this would be great 

 

pick below of gas assembly 

 

 

[BigStew]

are you sure its the m500 as that was a clone of a marushin shot gun which was just as leaky as the clone