Locksmith.

Stay fay away from China or Taiwan made padlocks. They don't hold up and sometimes duplicate keys can be hard to find.

Some American brand padlocks may be made or assembled in another country but the company makes sure that blanks and replacement parts are alway available.

I deal with this **** everyday. People buy these padlocks not realizing that nobody imports keyblanks for them. So we have to search our inventory of over 1000 keyblanks to find something close enough to work. It's counter productive as we may look for a blank for 10-15 minutes for a $2.50 sale.

We carry several major brands and over 60 different types of padlocks. Almost all of which can be keyed alike.

Some padlocks are rekeyable and some are not. Non rekeyable padlocks can be ordered keyed alike in great quantity. But I recommend buying rekeyable padlocks. If you lose a key or someone gets a hold of one, you can have the padlocks rekeyed instead of buying new. Also keyed alike sets are sometimes discountinued by the manufacturer or distributor. Some locksmiths keep the same keyed alike padlocks in stock and sell them to anybody and everybody. Buying rekeyable padlocks keyed to a random key would be better.

You might pay more but it will be worth it in the long term.

Another option might be combination locks.