General:
* Ubiquitous
* Widespread
* Pervasive
* Omnipresent
* Found everywhere
* Readily accessible
* Universally available
* Commonly found
* In every corner
* At your fingertips
More specific:
* Globally available (if it's available worldwide)
* Nationwide (if it's available across a country)
* Locally sourced (if it's available close to home)
Figurative:
* As common as dirt
* A dime a dozen
The best choice will depend on the specific situation and the tone you want to convey.