Here is the list of things needed for a nappy washing hose
1 mtr of 1/2 inch hose (garden hose ok)
2 x 1/2" x 1/2" plastic hose tails
2 x clamps to suit
1 x plastic garden hose gun nozzle
1 x Roll of Plumbers Thread Tape

This should fit to your tap behind the toilet and you should be able to get all of that for around $20 from any hardware or bunnings type shops.

Assembly:
place clamps over hose ends
place hose tails in each end of hose
(if this is difficult, put ends of hose in a cup of hot water for approx 3 mins each to soften hose)
Tighten the clamps with screwdriver
connect one end to the tap fitting behind the toilet. and connect the nozzle fitting to other end of hose.
Make sure each end is firmly fitted and turn the tap on.
Make sure to check for leaks. If you have any leaks from the fittings you may need to use "Plumbers Thread Tape".

This is what i was told Phoenix - let me know if you try it.