Wow.. I missed this one
Hi mate, welcome to the Japan forum
For car parts, check out Yahoo auctions Japan for (non-electrical) anything you need, I've bought tonnes of stuff from there and 99.9% of the items have been excellent, real bargains. Other than that, try Autobacs 'Seco-han Ichiba', they also have majorly reduced prices on lots of new 'out of production' stuff... seats, wheels, tires, exhausts, electronic goods you name it. It's like a SuperAutobacs 'outlet' shop.