Hey! I'm Madeline, and I only really have one that would know of Isadora is Geoffrey Nott - one of the Inner-Circle Death Eaters, currently a high-ranking hit-wizard in the DMLE and a second-tier Pureblood. He's pretty much boring on the whole and quiet since his Selwyn wife died, but he lightens up a bit when you mention his son Theodore. He's all business :P
And the rest are Caradoc Dearborn - douchey boy in hiding from the Ministry and reluctant Order member, and Barnabas Cuffe - equally if not more douchey Daily Prophet writer of Culture articles and part-time "piss people off"-er. . .if that's a title, that is. Not much with them, I'm afraid :P