Aristo-Craft make two smaller diameter circles of track.
A11140 is a 20" dia. circle and
A11145 is a 31" dia, circle (which is made principally for encompassing barrels at Christmastide.)
They would be technically compatible with LGB but not visually so.
Bachmann UK, the importer, lists the 31" as in stock but not the 20" version. A good many dealers sell for less than the price shewn on the Bachmann web site. It is worth remembering that sleepers on real railways are not always the same in some sections of track: that, however, depends on the place and era you wish to model.