Best solution is this but not sure if you'll find it locally
http://www.jlaquatics.com/product/pp...+Solution.html
You could use saltwater provided you're confident on another device to measure it's salinity/SG however you will be introducing some kind of error but who knows if it'll matter. Pretty sure 53mS = 1.026 SG @ 25C
Otherwise perhaps someone has some fluid they could lend you.