For those who use the search function in the future, and need this information, the A wire is power in, the B is flasher out, and C is a ground.
If you are looking for a cheap source for the solid state 24 V flasher, good luck. They are somewhat expensive. You can find them on ebay, or if you know of any wrecked MLVWs they use the same flasher. Perhaps prefair surplus, who recently wrecked a bunch of MLVWs, will sell just the flashers at a reasonable price.
http://cgi.ebay.com/ebaymotors/Flash...Q5fAccessories
http://cgi.ebay.com/ebaymotors/Flash...Q5fAccessories
As an alternative, you can wire in a standard thermal 2 prong 24V flasher by running the A wire to one terminal of the flasher, and the B terminal to the other. You can do this with a 3 prong flasher as well, but remember that the third prong is for a indicator lamp on the control lever, and is not a ground. So do not hook C to the third terminal.
The prime killers of the solid state flashers are heat and short circuits. A pinched wire at the frame will equal a very short flasher life. The stock position for them, right near the exhaust manifold, is not ideal either.