TheUrbanEntity mentioned Peter Loughran and he may be a good option but, I would suggest you think of it this way - decide what it is you want and how you want it to function. Draw up designs with measurements (or approximate measurements because, ya know, prototype) and then decide what this 'thing' needs to be made out of. Metal, wood, plastic, electronics, etc. Then, find someone (not necessarily a magician or a creator of magical things) that specializes in that field.
You need metal? Find a machinist. Wood? A woodworker. Plastic - someone with a 3D printer and software. If you need electronics, you can hop on a maker forum and find someone that'll make you something. Befriend them, give em some money and work with them to hammer out a prototype. Try it for a little while and then refine it. See what's wrong (or what could be better) and make necessary adjustments with whomever you've commissioned to create this thing.
Once ALL of that has been done and you've worked out kinks and you've actually been performing it for a while, you have more than just an idea - you have a real working proof of concept for yourself. You can then take this to a manufacture that you decide on and have them produced in quantity. You could even contact Murphys, T11, and other magic distributors via their 'submit a trick' and if they like it, they'll work with you to produce what you need to sell it in mass.
Good luck man! Can't wait to see what you're working on!