Welcome mate,
Hope your IS200 gives you many miles of happy service- I'm running an 10 year old IS200 with 140k on the clock (100k done under my ownership) without any problems.
1. OEM mats are no longer avaliable from the dealers, pretty certain you can't get a OEM bootliner from the dealers either now, but I'd check...you never know...there might these items lying around in some dealers stock room?
2. Tyres- Most people for go for Falken FK452's as the Lexus specific Dunlop SP9000's are no longer available. Goodyear Eagle F1 Asymmetrics are also a good tyre (expensive though), I had a set of these, very good tyres. I'm currently using Yokohama C drive's atm, they are also wearing well.