Hello
You can buy it from the oldman at magic lake. Of course it confusing at first because he dont call his stuff with an actual name. Sorry I forgot what is butt plug named, so you need bruteforce every item he sold.
But when you choose the item there is comment from the MC like "it's seem like buttplug or glasses etc". I reccomend to do quicksave and load in case accidently you choose wrong item because all his item is really expensive and overprice.
ohh yeah if my memory serve me well the price is $480. Of course im not 100% sure tho.
Okay GLHF