Hello,
my name is Samuel, I am a mechanical designer located in Montreal, Canada. I stumbled on your project by coincidence - as you might notice, I do not have a provider rating because I am just starting to use Freelancer to find freelance work, however, I have been a Freelance member for many years and have hired more than 20 providers over the years. My employer rating is 5/5.
Your project seems to be right up my alley. I have a mechanical engineer bachelor degree, with a specialization in Design & Manufacturing.
With this said, I have personally designed many industrial machines (in Solidworks) over the past few years. These machines have been built and are currently in operation at the customer's location (Canada & USA). I am employed as a designer in a design firm where we specialize in the design and in-house manufacturing of automation machines, robotics, industrial equipment and consumer products like your cell phone case idea.
I can assist you with all parts of your project: Design (concept, which you seem to have already), modeling, technical drawing for manufacturing, prototyping and even production. I have access to a full fledged machine shop for manufacturing any product.
Let's discuss - what material is your case to be made of?