Is there an easy way to do this? Alternatively, if I could get the width of the scrollbars, I could just use the dimensions of the ScrolledWindow and subtract them out myself...
Use wx.SystemSettings.GetMetric() with wx.SYS_HSCROLL_Y and wx.SYS_VSCROLL_X to get the scrollbar sizes. Then use window.GetClientSize() and subtract it out.
http://docs.wxwidgets.org/stable/wx_wxsystemsettings.html#wxsystemsettings
>>> wx.SystemSettings.GetMetric(wx.SYS_HSCROLL_Y)
16
>>> wx.SystemSettings.GetMetric(wx.SYS_VSCROLL_X)
16