Laptop parts are as much available as any used desktop part. The difference being each part is usually specific to a particular model. So you have to get the exact part. While a desktop you can usually get away a part form a same model series.

After a little search I'm guessing that you actually have a Satellite A100.
If this is the case there are several resources that have parts.
satellite a100 motherboard - Google Product Search
toshiba motherboard laptop - Laptop Accessories - BizRate - Compare prices, reviews & buy - Price - ReviewV00006800 - Toshiba Satellite A100, A105 Series Laptop System Board (Motherboard) - Laptop System Boards for Satellite A100 Series