Drill into concrete with no space for a hammer drill

Hi, I have to put up a curtain pole and on one of the sides there is a fit in wardrobe that cannot be moved. As a result, there is no space for drilling the holes using a drill. The holes seem to fall right on to the window lintel i.e. concrete and I am not sure how to do the holes. I have read about angle drills, but most of them seem to be suitable for either wood or steel and not concrete. I am unlikely to need to use this very often, so spending the money to buy one seems like a waste. Renting one is expensive £35 a day, so I am not sure if there is a way of doing this by hand or any other alternative Thanks, Luis