You can do a search online for the contact number. I probably have violated the advertisement code here just by naming them openly - let alone give a phone number!
I don't see any P31 in Singapore anyway at this moment so no matter how much you want it you may not be able to get it - but do try your luck with the distributor. By the way, on its own, P31 mobo is less than $100. P35 is about double that - you're correct. IMHO, if you buy an old chipset like that probably you should just use onboard graphic (any specific reason why you want 4650?)
If you don't mind I'll give you a few more (unsolicited) opinions. You may want to reconsider about the whole principal of building a DIY rig: if you live here, you better buy parts that are popular here - not one that you read to be good. RMA will be a nightmare if you buy something that distributor does not stock (think a 3 month waiting period for example).
Secondly, mobo is your most important part aside from processor. So I'd put more money into mobo rather than buying a graphic card that is more expensive.
Last but not least, assuming you have budgetary constraint, you would be better off getting an AMD board and processor - you can get much more common board, and at the price of an intel board, you would almost probably get a much better AMD mobo (or conversely with the same price and board level, you would get a much faster AMD processor).
Good luck.
(PS. IMHO again, Powercolor performance and stability is not inferior to Sapphire. For that matter ASUS, Gainward, XFX, HIS, or Palit are all good if you can find their 4650 display board. You only need to be careful with new GPUs or chipsets (say if you buy 4870 or GeF 260) but for something as Radeon 4650 you can hardly go wrong with any of the above brands - just make sure you get the feature you want).
