Then you should consider this key chain available in Japan:

The key chain/gadget/toy is called Puchipuchi in Japanese. This - I am reading - is the sound of a little pop as well as the name for bubble wrap.
Puchipuchi is designed to mimic both the sound and feeling of popping little plastic bubbles. :-)

It is a constantly repleneshing electronic toy. Every 100 pops you are getting a surprise sound like a barking dog, door chime, or fart sound.
You can easily carry it around, for example on your keys or backpack zipper.
Their slogan is: “Anytime, anywhere, forever…you can puchipuchi”

The producer by the way is not just any Japanese toy company, it is Bandai, the world's third largest toy producer.

Here is the link to the Japanese ad on youtube.