How do I convert a wireless dongle into a USB transmitter? [closed]

I think my question is fairly simple, but I haven’t found something that works yet:

I have a wireless keyboard with a USB dongle. I want to plug that into something that can connect to a computer via Bluetooth instead of via the wireless connection.

The reason is that I have a Bluetooth keyboard connected to two computers, and I want to switch to a different keyboard, but the other keyboard is wireless with a dongle, meaning I would have to plug it into a KVM and plug that KVM to the two computers.

Is there a way to do this? I saw this but I was expecting/hoping for an off-the-shelf solution.