A quick google of the part number yielded several links. Here's one.
There I go again!! It seems everytime I buy a laptop, it is the model that requires me to go on a scavenger hunt to find a replacement battery. Of course, Toshiba's web site has the battery - for $169. I did a search to find a company that sold it cheaper. Of course, it seems these companies have every conceivable battery except the one I need. Does anyone know where I can get this battery for less than Toshiba's $169? The model number for the battery is PA3228U-1BRS. Thank you.
Have you tried ebay?
You could also quite possibly buy a weaker version of the battery for a lot cheaper. For the M200 for instance, someone posted here a while ago about ebaying a 3600 mAh version of the stock battery (which is 4400 mAh) for about $20. The voltage is the same and the shape of the battery is the same so its fully compatible, but the life of the cheaper batter is about an hour shorter, which I think is well worth it given the extremely low price. In the case of the M200, the model number is PA3191U-4BRS for the stock battery, with the "4BRS" changing to "3BRS" or "2BRS" for weaker versions. A little bit of research might turn up a similar scheme for your 3505.