Japanese help?

I have been collecting the Marmit Piggy banks, and one I picked up is missing the bottom stopper. I tried to find a match searching English language, but did not find a good match.

I know it's 50mm, so that will help me, but I'm not sure what japanese search terms I should use. Google translate has not really helped.

Anyone have a suggestion? Thanks!

 

Not specific, but might be good to start off with "円谷プロ 貯金箱" aka tsuburuya pro piggy bank

EDIT:
Including the word "marmit" and linking a google search here:

EDIT 2: Sorry I completely misunderstood your question. You can find 50mm piggy bank stoppers by searching "貯金箱 フタ 50mm"

 

Thanks! I'll give that a shot. I was searching for "stopper"
ストッパー and they were all black rubber

 

I wonder if you could ask Marmit (via Instagram) what he used for the bank stoppers.