Hi!

What should I use?

How about a cheap tape recorder? You could pick up a battery operated
unit very inexpensively secondhand (and for not much more brand new).
It's cheap, simple and a (still) large installed base of tape players
means you can play the recording almost anywhere.

What you really want to do is look at the microphone you are using. I
think you'll want a microphone with an omnidirectional pickup pattern
and the ability to pick up sounds from afar.

Unidirectional and "noise canceling" microphones are probably not
going to work well for this application.

William