The Henry Squire The Toughlock Re-Codeable Combination Padlocks have die cast lock bodies with solid steel shackles that are stronger, heavier and cheaper than brass equivalents with no keys to lose.
There are 3-wheels on the 20mm and 30mm versions offering 1,000 possible combinations. There are 4-wheels on the 40mm version giving 10,000 possible combinations.
Consider the value of property to be protected.
Choose a padlock of suitable security rating.
Use a padlock fitting (ie hasp and staple, padbar, chain etc.) of equal strength to the padlock.