Have your doctor make out prescriptions using scientific names that are understood internationally. Bausch and Lomb and Barnes Hind contact lenses along with cleaning solutions are sold by competent optometrists in larger cities and major tourist areas. Unless you are entering Indonesia from an infected area, you won't be asked for your International World Health Certificate. If you want to stay in a hostel, just pay the few dollars extra. Counterfeit ones sell in tourist's places in Southeast Asia, but be careful of poor forgeries.
Indonesian officials wary of fakes.
They may require additional identification and that you are no older than 26 before giving you a discount. Make sure to include your date of birth, citizenship, and name of school or university where you are a full-time student. Do obtain an International Driver's License, valid for a year, from your local Automobile Association. You never know when you'll want to rent a car or van. Get an IDL with a motorcycle endorsement if you plan to rent a motorcycle on Bali.