There's a place North Fredrick Street/Parnell Square, D1 that does domestic appliance parts although somebody here a while back said that they weren't the most competitive. However I've used them a few times for various bits and pieces. I think there's another place up on Dorset Street but I can't remember the address...
There is a little kiosk Stillorgan shopping centre that sells electrical bits and pieces. I got a dishwasher cutlery holder there a few weeks ago for about 17 euro, the official zanussi one in a zanussi spare parts place in Clondalkin was about twice that price.