Depends on the age of the Panda:
older, with points are OK.
Search google, you'll find things like
http://martingriffith.users.btopenworld.com/TACHO.HTM
http://www.3riversjunction.com/Auto/Tach/tachometer.htm
or even
http://www.maplin.co.uk/
and search for K2625 on the site.
if you're a dab hand with a soldering iron...
later fuel injected Pandas could be more problematic, if it has two coils... even then I suppose you could fit a tacho which is designed for 2 cylinder 4-stroke with connection to one of the coils.
Which is something I should of thought of months ago when the query was raised elsewhere :-(
Regards
John H