I think there aren't other ways for that.
normal TSQL Backup Skripts only allow to backup to local disc.
If you have enough space you could make a SQL-Task which makes a backup on local disk and after this move it via powershell to a UNC path.
if you don't have enought space for this:
with the following you can activate xp_cmdshell again...
-- To allow advanced options to be changed.
EXEC sp_configure 'show advanced options', 1;
-- To update the currently configured value for advanced options.
-- To enable the feature.
EXEC sp_configure 'xp_cmdshell', 1;
-- To update the currently configured value for this feature.