Here are the two choppers. They are made by Genius. Google you can find them. If you have a Kitchen collection outlet they have the choppers.
The 1/4 x 1/4 i have had for bout 5 years. The canisters on both just rotate out from the tabs.
1/4
Blades are fixed, You just push down to cube.
You can take the plate out by pulling the 2 locks together as shown. This is the 1/4 plate
Here is the 1/8"
The plate and blades stay fixed, you pull an insert from the bottom.