The place to start is what materials make up your prototype? If it`s a regular blind, you`ll have metal, fabric, twine, plastic. Then it`s can use use `standard` sizes of materials or do you need custom fabrication. Then you need to identify sources for these parts, standard or otherwise (online is a good way). Then you`ll need someone to fabricate the pieces (probably from dimensioned drawings or sketches). Then you`ll need someone to assemble the pieces. Viola! Window blind. Depending on how `handy` you are, you may be able to do some or all of the work yourself or find a mechanically inclined person in your neighborhood. High school or college mechanical design, woodshop, metalshop, and autoshop classes are good places to start. Also, many areas have local `inventors` clubs that get together to share ideas. They could probably help you get started locally.
Other route: Find someone to design it down to the dimensions of all the component pieces. Then get electronic copies of the drawings of each piece and the assembled blind. Then do a Google search for local or domestic or overseas prototyping houses. And send them the electronics drawings and ask them for a quote to make how many you want. You`ll probably pay a large `one time` fee for them to `setup` the job, then a smaller per unit fee after that. You`ll want to get references from existing customers who had work similar to yours done.