It is very easy to make it.Basically this is Glutaraldehide and you just need to make 2,5% solution.You can get 500 mls of the 50 % solution from here: http://www.merck-chemicals.co.uk/ and dilute it with 19 parts RO water you will get 10 l of 2,5 % solution.
Yes it is toxic, so you need to be...