How did Pawbert get his paws on Ebenezer's Venom Injector?

I always found this detail odd because it's not something you'd think the Lynxleys would pass down the generations. Not when it could potentially expose Ebenezer's crime like Agnes' patent.

I'd understand if it was a new injector, Pawbert could easily have bought it. But I'm pretty sure it was confirmed to be the same one.

Also, where was he keeping it? It's pretty bulky yet until Pawbert uses it there's nothing to suggest he had it stuffed in his pocket.