So I ordered this replacement battery from Amazon, received in 3 days.
The model, very well packed, proves perfectly compatible with the Bosch 12V series of drills, and, surprise, it is a bit larger in height than the original battery, but this is likely due to the fact that the battery capacity (3000 mA / h) is higher by at least 50% than the original batteries. After the first full charge (essential) there is indeed impressive power on the drill chuck. The life of the battery will be several years, provided the charge periodically (at least every 3 months in case of prolonged non-use) because like all NiMH batteries, it loses about 10% of its charge every month and you should never leave completely discharged.
I am very happy with this purchase, especially as the price is reasonable (under 30 euros).