Seriously, Chill60 is right: you need to talk to ProCore themselves, and see what they can do to help - it may be that they can point you ate good developers with experience, or pass your details to them to see if they are interested.
Alternatively, there is always
Hire Freelancers & Find Freelance Jobs Online - Freelancer[
^] which specializes in putting those needing development in touch with developers. But ... be aware that are a lot of substandard script kiddies out there - if you pay peanuts, you will get monkeys!