Wiki images should be back once the wiki update is done; Simon's working on it.
The Jawa ignition is no more complicated than any other CDI. I personally think it's much simpler than the typical CDI, as the magical black box is a super simple, well understood circuit.
A thyristor is a readily available part often used in power electronics, typically constructed in either a PNPN stack or as a cross-coupled NPN and PNP BJTs. Think of it like a transistor that latches on when triggered.
It looks like the thyristor used in the circuit on the moped wiki is an On Semiconductor MCR106-6G; they linked to Newark, who doesn't appear to sell them anymore (always use the manufacturer's part number, not a distributor catalog number, folks!). Should run you about $0.60 from digikey or mouser. (edited)