Given the walking varminter is fairly new to the market it's highly likely you're venturing into virgin territory. Typically there are two screws holding the pad on - one at the top and one at the bottom - but they could be glued on as well. The buttstock is hollow though so I would lean toward it being attached with screws.
As far as finding a replacement, it will have to be a grind-to-fit and you might run into an issue if it's recessed into the buttstock a little.
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