I'm sorry to hear you've misplaced your Soundbar 700 universal remote. In order to change the Wi-Fi over, you'll need to put the soundbar into setup mode for it to be found in the Bose Music app. This can only be done by using the TV Icon and Skip Back button combination on the remote. Therefore, I'd have to recommend that you reach out to support in order to obtain a new remote.
Once you get a new remote, you can pair this with your soundbar by following these steps:
If the remote is not already showing the top source buttons flashing, then simultaneously press and hold the Volume - and Left arrow buttons for five seconds. On the soundbar, press and hold the Action ○ button for five seconds. Then wait 15 seconds for the remote and soundbar to pair.