I'm currently working for a client involved in the Public Private Finance and Public Private Partnership industry. They want to generate more visibility within this community and as part of the marketing strategy construct a reciprocal link campaign within this theme.
I have managed to find a few possible link partners but the majority of sites dealing with this theme are governmental sites or organizations which are averse to linking to corporate sites.
The main advice I'd offer is: 1) Keep looking within your topic - some categories have lots of opportunities, others take sifting through many sites to find a candidate. 2) Consider some general sites and directories - DMOZ, Yahoo, and smaller compendiums of sites.
Beyond that, there has been lots of discussion here about creative ways to get links, like writing articles about your topic and letting other sites use them if properly linked.
They have been submitted to all the major directories and are listed in Dmoz, it's just that it's such a specific theme. I guess I'm thinking to literally when I need to climb out of the box and come at it from a different angle.