Repco, Auto 1, Autobarn, Coventry should be able to supply with a kit, youll need year of car etc, not sure on cost, should only be few dollars
I generally use about 3 to 4 bottles of Shell brake and clutch dot 4 fluid and give everything a good flush out
Check your booster for leaks also, get a mate to listen for you while you apply the brakes or visa versa or connect a T piece to the vac line with a pressure gauge attached
See how you go..........