Sorry theres no such aftermarket product for that bike. In fact you'd be lucky to find stock replacement parts for that old of a bike. The motorcycle manufacturers are only required to stock parts for 10 years.
Happy bumpy trails!
Was your bike equipped with CDI or are you looking to convert it?
If it was originally a CDI bike then your friendly neiborhood Honda dealer can probably get you a replacement unit.
('78 isnt THAT old.) Plus the 125 Honda thumpers were very popular motors.
Parts should be easy to get.
My '82 XL500r is turning 20 and i can still get most any part i need for it through my local dealer.
Just talk to a dealer who isnt prejudiced against older bikes.
Just found out that my local Honda dealer is NOT old bike friendly. They will not work on anything older than 1980. They don't carry any ignition parts, and the carb parts are unavailable, according to their computer program.
TGR , try another dealer.
Although it IS possible that those parts are obsolete it IS also possible that that particular dealer either:
A- Is too lazy to hunt for the old microfischs on your bike.
B- Would rather see you get frustrated trying to fix up that good old machine, and buy a new one from him. (what to do for parts on that NEW one in a couple of years, eh???)
C- He could just be "old bike predjudiced" and want to see another good old faithfull Honda XL go down to the scrap yard. (where are these new hightech wonderbikes gonna be in 10, much less 25 years?? huh?)
If they are truly gone, there are always plenty of salvage yards out there to search thru not to mention lots of bike shops that specialize in parts for our beloved older machines.
If it ever gets back online try xlintperformance.com for a start.