Custom vehicle door chime

Hello! I have a project I'd like to find someone to build a prototype for. If the prototype turns out well, I may request to order a larger quantity after final revisions. The idea came from this video: [login to view URL] I would like you to design something similar using a mk2 (1984-1992) Volkswagen door chime relay, or equivalent. You could retrofit an old relay, but what's really important is the plug type, and the dimensions. If you can create a functional, high quality product from scratch, even better. There are some key features I would like to the device to have. 1. Ideally, this would fit within the existing relay housing. If that is not possible, follow up with me and I can provide more details pertaining to size or port placement limitations. 2. The user should be able to easily change songs via microSD with a card port on the relay. (microSd should be able to hold at least one song.) 3. Should there be multiple songs on 1 microSD, the songs should be played in order, starting a new song each time the relay is activated. 4. The unit should have an easily adjustable volume rheostat. 5. Should be able to produce in small quantities. 5-10 units. Resources Idea video: [login to view URL] VW Relay: PART # 321 949 433 B - ALSO 5SA 005 017-00 ([login to view URL]:g:AiQAAOSweRVe0AOf) Custom Chime with microSD write-up: [login to view URL] Different vehicle make, model, and relay, but similar functionality desired. Budget: $150 for Research, Development, Prototype and 1 Revision $50 per unit for final product. Prices Negotiable, willing to pay more for development if final version is reliable, but low cost.