Punches
With a compatible punch, you will be able to continue using your William Hannah notebook for years to come.
There are a number of punches available - some I have tried, and some that I have not but have heard are fine.
I will give details of the ones I know below, but you may also want to join the William Hannah User Group over on Facebook to learn and share more about compatible punches.
Atoma
Perhaps the second most compatible punch (after the ADOC below). Personally I think it's a bit pricey, and I broke the first one I had within a day by trying to get it to punch a piece of cardboard, but I know many customers use them very successfully for punching paper.
ARC (by Staples)
A good value, slightly more heavy-duty punch, but getting quite difficult to find these days I understand. The 'mushrooms' are more rounded, but not enough to cause any issues. Again, a popular customer choice if you can get one.
Levenger
I have never used or seen the Levenger punch (it's sold in the US, and mostly used by US customers), but customer feedback is that it works well, and it has a similar profile to the ARC punch I understand.
Craftelier (Happy Planner)
A cheaper punch that still seems to work well. I have tried the 11 hole version and it worked fine. It has a longer 'stem' to the mushroom, and I wonder if if that will cause minor page-turning issues when mixed with our punched paper, but I have also seen positive feedback from customers, so perhaps not an issue.
And the one I used....
ADOC Punch-Ex Prof Puncher, available here
This is the brand of punch I have used for 10 years. It is expensive, difficult to find and very heavy-duty. It also not without its challenges - I have to make multiple 'adjustments' to a new punch to get it to work without issue. I really DO NOT recommend you get one - it is complete overkill for a personal user - but I am adding it here in the spirit of transparency.