1) First, selling something doesn't always have to be through testimonials or referrals. If your product -here commercial office space - makes sense, then, people will be interested. When I started my marketing agency, the first client I acquired was a big LED supplier in China and I did it by:
a)Giving a practical solution to his problem
b) Being professional at every front
c) Referring to my industry experience (not clients)

2) There are many things you can do to connect with potential clients in your local region. Here are a couple of them:
1) You can highly target ads in your region
2) You can create a killer office space introduction video
3) You can channelize your current network to get introductions

I think reading this B2B marketing blog I wrote couple of weeks ago will help you:
https://www.upreports.com/blog/marketing-growth-strategies-hacks/

Need further advice? I'm just a call away!