IT system house seeks web tool

We are an IT systems company with over 150 employees at several locations and are looking for a web tool for our main location with the following requirements:

• It should support scheduling - instead of opening multiple calendars in MS Outlook, the web app should use a search mask to suggest suitable employees based on various possible criteria (e.g., topic, customer, area of expertise, time required, department).
• The planning itself takes place via MS Outlook; the tool is only used to find available capacities.
• In addition, graphical views of the workload of individual employees or departments should be offered for evaluation.
• The tool should receive input from an existing SQL database.
• As finished software.
• On-premises

With regard to the number of software workstations, the tool is to be provided as a web application in the company's own MS SharePoint for approximately 10 employees. The tool is to be used in the user help desk.