What roof bars?

[moray]

Hi folks, I've just bought a 1.6 multispace desire with factory fitted roof rails and I need to buy roof bars to span across them for carrying ladders. Citroen ones i know I can get but they are a bit pricey and Im hoping to get suitable ones from ebay, the thing is the roof rails have sort of metal bracket things under them (kind of hard to explain,they are about an inch or two long and at each end of the rails) Does anyone know what bars I can get that will fit these??

Any help would be greatly appreciated

Thanks