Hi there, just did some Googling, and found a video where a demo talks about it, She shows a catalogue pic, and it says the staples are 3/8th inch long. It also calls it a mini stapler. I have a mini stapler,( just a generic one) it's staples are that size, and they have Size 10 on the box. I'm in the UK, so I don't know if you have a different sizing system over there? As it describes it as a mini stapler, I'm wondering if the Tim Holtz ones for his Tiny Attacher are the same size? Just looked on Amazon.com, and your sizing is the same as ours. Try this
LINK to see whats available.