react-native - require() must have a sing string literal argument

I'm writing a sampler app in React-Native using Expo and have run into the follow error:

react-native - require() must have a sing string literal argument

Pre-recorded samples are played called like this:

const SAMPLES = [
  { name: 'air horn', uri: require('../samples/air_horn.mp3') },
  { name: 'rim shot', uri: require('../samples/rimshot.mp3') },
]

  playSample = (uri) => {
    const { soundObject, status } = Expo.Audio.Sound.create(
      uri,
      { shouldPlay: true }
    )
  }

It's somewhat based off the Expo documentation and works fine. However, I also want the user to record their own samples, which means it's coming from a custom URL:

playCustomSample = () => {
  const customSample = this.props.navigation.state.params
    ? require(this.props.navigation.state.params.custom.toString())
    : require('./samples/blank.mp3')
  try {
    const { soundObject, status } = Expo.Audio.Sound.create(
      customSample,
      { shouldPlay: true }
    )
  } catch(error) {
    console.log('ERROR:', error)
  }

When I log the custom param I'm being passed by navigation, it's there. So I get that I'm doing it conceptually wrong--that require() requires a string, but I'm not going to know the name/location of the file until it is recorded.

How would I get access to the audio file without knowing the link ahead of time so I can include it?

Also, I don't have access to a Mac so ejecting it from Expo, so using something like react-native-audio or react-native-sound isn't an option.