Except for one time at Cowes and one time at Newhaven, I always stay in the Cabin's at San Remo Holiday Park. Give them a call, I doubt it, but you might get lucky
http://www.visitsanremo.com.au/holidaypark.html San Remo is right next to the bridge to the Island, has everything you need, bottle shop, restaurants, supermarket, laundromat, two pubs (live bands every night). It's the start point for the Island Shuttle bus so you always get a seat to the track

Your Bus Ticket also gets you to Cowes and most other places on the Island, so we just lock the bikes away for 4 days and get on it

The Sanny Pub gets pretty packed on Friday and Saturday nights, but nothing like the sardine tin of Cowes.
You may not be too late for Island accommodation. Ring the Phillip Island Visitor Information Centre. They do all the running around for you and have a list of available accommodation on the Island, including late cancellations etc...
http://www.visitphillipisland.com/phillip_island_visitor_information_centre.html