Hi Tim! Wespe models from Romania offer two versions of the Schneider,former Retrokit models ,I've ordered directly at their site with no problems and pretty fast delivery to Germany.
Modell Trans from Germany do many WWI Tanks and conversion sets for Emhar etc..I have build the Sant Chamond which is cast as a solid resin block but features crisp detail.
For a wizard like you these kits shouldn't present any difficulties...
cheers
Mathias