Well size and shape have alot to do with it, also just search for laptop spare parts on Ebay. You can get a whole Laptop mother board for as little as £50 and the rest from £10 upwards. What I would do is find some laptop you like the specks of and look around on Ebay.
Also I saw somewhere that there are some some ware that some places do specialise on selling laptop type hardware you just have to look real hard for them, but give mini-itx.com - news
a try they sell small form computer parts they might be able to help you.