The title 'Spare Williams' doesn't ring an immediate bell for a major werewolf release, which makes me wonder if there's a slight misremembering there. Could it be a character name from a series like 'The Wolfkin' or something by Susan K. Hamilton? Sometimes our brains blend details.
My first instinct for tracking down niche werewolf audiobooks is to get granular on Audible. Use their search but filter by paranormal romance or fantasy, then comb through narrators you like—people like John Lane or Stella Hunter often get cast in those roles. Scribd's subscription is another solid angle; their catalogue is less predictable but huge, and you can sample a ton of shifter fiction there.
If it's truly an obscure indie title, the author's own website or a platform like BookFunnel is where the audio might live. I found a monster romance audiobook last month that way, direct from the author's Patreon. The hunt is part of the fun, honestly, even when it leads down a rabbit hole of similar-sounding titles.