I have a quick-release lever on the forestay, although it's not a Highfield. Johnson Lever maybe? The same one
@Hardhead posted. It was a direct replacement for the turnbuckle, no new forestay needed.
I don't like them on the forward lowers. You have to unpin them from the chainplate to adjust them, which makes rig tuning a PITA. And I mess with the rig often, including under sail when conditions change.
But I can live with this characteristic on the forestay, since the backstay is adjustable.