Require a Manufacturer that can produce a cellphone prototype

Hi I need someone to assist me by sourcing a supplier that can do a cellphone prototype. I require a demo model of a concept that i am working on. The supplier/manufacturer needs to be reliable and not charge a small fortune. The requirements of the cellphone and features will be shared with the successful supplier/manufacturer. Note that I only want one prototype for now. I am not looking for mass production of the cellphone only a demo/prototype. Once this has been done, I will negotiate with the supplier/manufacturer and provide them with sole right to produce the cellphone for mass production. Please respect the budget that I have for this- I am only requesting a reliable supplier/manufacturer and not a massive job.