There are so many booking sites to choose from these days. If you are visiting Yarralumla and want to stay nearby, in addition to searching bookings sites for Yarralumla you can search for Deakin, Barton, Kingston, Woden as they are all close by. The city offers a wide range of choices and is only about 5 kilometres from Yarralumla.
The Hyatt Hotel on Commwealth Avenue is the closest hotel.