Issue with Syncing Audio from DNG Sequence to HQ Source

Hello! Recently I shot a video in which the camera output clips as a .dng sequence with a matching .wav (low quality; straight out of camera). I also recorded audio externally for a higher quality source, to sync to later. Unfortunately, I cannot seem to find a way to sync the audio tracks, as the sync feature is grayed out unless one of the inputs is a 'full' video clip (audio and footage in the same file container). My thought was that I could sync the high quality source to the low quality and then group them and line the low quality up to the .dng sequence, but it doesn't seem like that will be possible. Any suggestions are greatly appreciated!