We are seeking to bring in someone at a founder level that is connected in the Silicon valley investment circles. Is there anywhere in particular we could advert to see if anyone fits our group? Any recommendations appreciated.
In my (admittedly limited) experience, you won't find the sort of person you are looking for answering ads in the first place. You'll likely have more success growing your network via events like Startup Weekends, Hackers and Founders meetings, tech conferences, etc. and then working that network for good leads.
What do you need - money or a co-founder?
If you've feel you have the team you need and are just looking to access funding, go looking for funding. I know very few stories where one founder's only there for 'investor credibility' that have a happy ending.
If you know your team needs to grow because there are skills, experience or characteristics you're going to need and don't yet have, get out and socialise your concept (or business, if you're already up and running) wherever people gather and look for opportunities. When someone connects with what you're doing and has what you're looking for, you have a prospective new team member.
So suppose you're in the latter case and it turns out the line of well-qualified people who want to join you stretches right out the door. Well, I guess you're going to prefer someone who has that investor connection. But even if you draw a blank, you can now look at the shared problem of accessing investors, as a stronger pitching team.
If/when you're near Palo Alto, eat lunch at Stanford GSB's cafeteria. You're bound to run into someone.