When a fellow ASW-15 owner in my club lost some of his pins I bought a couple dozen of the AN safety pins mentioned in the LBA AD from Aircraft Spruce.. More expensive than the Walmart option but better? Not really. The Schleicher TN on the AD offers a pin part number to order from them the same style of pins you got at Walmart and says right in the TN that they are Ford parts. For some reason when my ASW-15 came over from Germany (1998) it had AN type pins on the airbrake connections (which use the up/down wedge L'Hoteliers) and the bobby pins on the ailerons (which have the rotating type L'Hoteliers). Another club member who has just bought an ASW-20 has been looking for the captive safety pins referred to in the AD as Schempp-Hirth pins - an ASW-19 in the club has them and they seem like a really good solution. So far no luck in finding a source for them.

Up here in the Great White North we frequently use the aviation department of Canadian Tire for our needs.