I tried to contact Ken(?) at the link Grumpy provided a year or so ago and he never responded. Perhaps is different now - I think he was going through some health problems at the time. I ended up buying them off the internet at 3-1/2" Seam Ripper 608
I paid ~ $1.25 each - it looks like they've gone up a little bit. There is a discount code (thankyou) that will get you 5% off. You my be able to do better elsewhere.