To rent a bike use Nextbike. Find a Nextbike station in Weissenkirchen next to the train station or bus station. You have to register via e-mail or phone.
For further information see www.nextbike.at.
You can also rent a bike in Spitz at Wachau Touristik Bernhardt. Contact the company via phone
Further information also available at tourist information Weissenkirchen.