I'm having trouble seeing what the boots look like from online imagery, but are the liners simply done up with a "cord lock" type of device?
Ah. Thanks for that, Mark. The correct term appears to be "lace lock", and it's more or less the exact same thing, but flatter (otherwise the lock would be pressing on the front of your foot -- because it's for the inner liner -- which would be extremely uncomfortable). In fact, the lock is Y-shaped, where the cords come up through the bottom, and then the lock slots down in between the cords where they come out through the top.
Unfortunately, searching for "Northwave" and "lace lock" reveals that they break quite easily and that Northwave's support is near non-existent.
I'll take a look at the cord lock / lace lock suppliers and see if I can find something suitable.