Is it permissible to take the difference between the wholesale price and the market price for an electrical part when I am commissioned to buy it for work, knowing that there is a specialized purchasing committee?

You are not permitted to take the difference between the wholesale price and the retail price, and you must return it to the entity that commissioned you to make the purchase; because you are their agent, and any increase reverts to the principal, not to the agent. Furthermore, your telling the seller that you have a shop when that is not the reality is considered a lie, and lying is forbidden. You must repent and seek forgiveness for this sin.