A quick search of eBay using "xs400 maxim ignition" found 3 TCI modules advertized as "CDI Box" by Grimm Cycle Salvage for $150.50US each. I noticed that all 3 had the factory ID sticker removed, which makes me suspicious. As with all electrical parts, Grimm offer no warranty but claim to replace defective parts... It's your $, you decide if you want to deal with them.