Here is an example similar to the part I have seen off a Subaru. The one I got came with a VW Jetta TDI that had a failed mechanical vacuum pump and this electric pump was powering the brakes. It worked great!
https://www.ebay.com/itm/31519333530...Bk9SR8q31KPMYw
This one is $49 on ebay. I am sure similar pumps exist on ebay in France. (Sorry, I said Italy before, for some reason I had that in my mind as your location. Apologies!)
All you have to do is wire it to a sufficient power source that runs whenever the key is on. If it were me, I would probably build a simple circuit using a 4-pole Bosch-type 30A relay with inline fuse direct from the battery, with the relay energized by a wire tapped off the injection pump solenoid which is hot whenever the engine is running. You don't want to overload that circuit to actually power the pump -- hence the use of a relay.
