I would strongly suggest trying some freelance sites, such as freelancer.com, upwork or even fiverr.com. It depends a bit what you're looking for, of course, but I myself have had great success on these.
From the posts so far it seems that very few people on here are aware of just how many freelancers are out there, who are just starting for themselves, or doing consultancy work after hours (with their employer's blessings!) You can find excellent freelancers who will work their arses off for you if they understand that you are in the startup phase like themselves. (Not to be taken advantage of, of course
)
I can quickly list some of my past experiences:
I had an enclosure designed from start to finish by an excellent mechanical designer in the UK, ready to be injection moulded. Paid £750.
On another occasion I had an expert iOS programmer make me a compete app from mock-up to launched app for £1200.
I had someone route a rather compact PCB for £360 - an expert EAGLE user who only charges $15/hour (I also used EAGLE at the time, but didn't have the time to route it myself).
I had someone make a website as a close copy of another website that I liked the look of, but customised for my business. Paid $250.
Mind you, I have also had some less than successful projects with other freelancers, who despite great feedback from past clients were completely clueless....so vetting is important! Either interview properly, or run a small $50-100 project to start off with to see if the designer is any good before committing to a larger project. Also be wary of large companies that move work from one to another. Be sure you interview the same person who will actually do the work! (Should go without saying, but...)
I have found that freelancer.com is great for PCB layout work, mechanical work and programming. fiverr.com is great for super small design work like a logo, business cards, slide templates, etc. When I need an expert embedded programmer I use upwork.
Good luck!
P.S Edited to add that on Freelancer (and possibly upwork) it is SUPER EASY to add an NDA to the agreement, and make the bidding round hidden, etc. It costs a little extra, but especially the NDA is very important.