Sam! Just walk in on Friday morning, about 8:30, and see if they have any cancellations or group-size reductions. If not, check again at 9, etc. At 11 AM. the no-shows become available. You are pretty sure to get one.
Or keep checking these links:
Day UseOvernight UseNote:
You may need to open the two links in separate browsers. The website gets tangled up when you try to check both day and overnight simultaneously.There are currently 5 day-use available for Friday.