How do I unpair a trackpad when the iMac it is paired with is dead?

Hi!

My iMac seems to have died (can't get it to boot) but I have a MacBookPro. Now I would like to use the Apple trackpad and keyboard that I used to use on the iMac on the laptop. They are both first gen (no lightning port).

When I try to pair the trackpad with the laptop it does not show up as discoverable. In the support articles I have read it says if the green light on the device flashes it means it is discoverable but if it is steady green it mean it is paired with another computer and I must unpair it first on the other computer.

This can't be done as my iMac is dead. Is there another way to unpair it?