The ones from Tayda are the same style (and, from the small pictures, look to be the same quality) as the ones Franky keep. They're also available at Rapid:
http://www.rapidonline.com/Cables-Connectors/4mm-StackableTest-Plug-83049I'll stick with the ones from Franky unless I'm making an order from Rapid, I know the quality is good.
Funny how they're cropping up everywhere (I looked long and hard for sources other than Rapid a while back) since Franky started stocking them for me.