I have a lost transponder key in the house.
Is ther a device which I cn use to find it.
Since my car can recognise it from a few feet away, it stands to reason the technology exists to have such a device.
Short answer: No.
Long answer: You could probably get someone to make you one, but you’d spend enough to buy several hundred (at least) replacement transponders.
They do make a keychain that responds to hand clapping by beeping. But you’d have to find your transponder key first in order to attach it to the keychain.