In general: every transformer from a DC model train will do. Most transformer from Fleischmann / Roco / TRIX / LGB / Märklin Z and some transformers from Lima were made by Bühler or
TITAN. Bühler stopped producing transformers for model trains, but
TITAN still produces transformers.
TITAN makes a transformer specially for LGB, thus also for Playmobil electric trains.WARNING: Never use a Märklin transformer for Playmobil electric trains! These are AC transformers, and will damage your train.
Tip: In Europe power is raised from 220V to 230V. If you buy a second hand transformer, look on the backside of the transformer if it is build to suite 230V. If not, the current on your model train layout will be too high.