Hi Ragdoll... allow me to be the first to say - 'welcome back!'. As rare as these cars are, they still do tend to come up for sale fairly often. Three places to check continually are eBay, Craigslist, and Hank at Paradise Automotive who runs the site ascmclaren.com who many forum members here have had positive results dealing with. His site has a 'Cars for Sale' section which seems to be updated regularly.
I'm sure others here have additional recommendations on places to check. Cars.com and Autotrader.com occasionally have a McLaren pop up as well. Even though I already have one, I still frequently look... mostly just for kicks.
5K will actually buy a fairly decent one with patience and a willingness to travel for the right car. If you find one that's distant that you have a strong interest in, there are numerous independent inspection companies who, for a reasonable fee, will provide you with a comprehensive write-up and professional opinion of the vehicle, including all noted flaws.
There are also tons of buying tips, as well as maintenance and operational recommendations you'll find by searching the archives here. I know I can personally say this site has been an extremely valuable source of information... as well as frequently entertaining. Good luck finding your 'new' car!
