I need a web booking widget for restaurants

General information for the business: Our clients are restaurants and this work will be a single web widget for their sites
Description of requirements/functionality: A full feature doc can be available on request.

This job is for a small and simple UI/widget that can be embedded on any website with minimal effort (i.e. a single tag preferably). It is a booking widget for restaurants, where the user enters details and submits to book a table.

The widget needs to acquire data about the restaurant from an API (http+JSON) and based on that information display the widget. It will be the same code for all of our clients; each client will supply a unique id to your code which identifies them and books the table to the correct restaurant via the API.

Maximum browser compatibility is a must (including mobile). Would like to avoid any use of cookies or Ajax or asynchronous calls if possible.

Optional: a way of defining styling the widget on the client side.
Specific technologies required: javascript, php, html
OS requirements: Linux
Extra notes: A full feature doc can be available on request.