Now where do we get a... oh wait, it's evidently a US Model 1906 Light Cavalry Sabre, the last one for slashing before the M1913 "Patton" sabre for thrusting replaced it and the M1906 is at this scale more or less unchanged from the M1860 that in itself is a copy of the French light cavalry sabre, so you could get it from any 35th scale US cav, like the one from Miniart or alternatively from any 32nd scale French light cavalry of the later Coalition Wars, wouldn't make much of a difference at this scale, especially since it's on a tank and not wielded...
Best regards
Raoul G. Kunz