Avanpost have a small but excellent range of TYW cuirassiers that are apparently close to the 1898 Miniaturas figures in terms of heft and proportions. The only hiccup is that they are only available in resin as I don't think IL Miniatures - the Avanpost rep for Western Europe - can import the metal versions.
Otherwise, the Empress (ex-Bohemian Miniatures) TYW range is probably the best out there for the early period of the war and should work with 1898 Miniaturas, especially if you keep the figures in separate units. Both ranges use the same Ebob horses and should prove compatible despite the different sculpting styles.