bike rental in bucharest / romania

Hello,
two lovely friends of mine are planning to do a bike trip in Transylvania. They are two super nice girls who are now struggeling to rent a bike for an affordable price. They arriving in Bucharest on the 26th of July and have to return on the 8th of August (Flight back).
Do you have any ideas? suggestions? Or is one of you renting bikes?

Thank you very much....