If you don't want to buy one then rent it. There are a lot of electrical and electronics shops online that offer such service.
I'm not sure what you're asking for - do mean an impedance matching transformer? If so, they're only a few pounds each.
no. there is no such thing as a generic output transformer, each is sized according to power handling and specific tube/transistor characteristics. some even have additional windings to facilitate inverse feedback, gain leveling, or similar circuits. historically, tube power amps were designed according to the transformer selected because that affects many design parameters. considering the pervasiveness of transistor amp designs that do not use an output transformer, you would be hard pressed to find one in most toys or other electronics.
You don't normally need an audio output transformer with modern electronics. The old tube gear was high impedance and high voltage. The output transformer was needed to convert the 3000 ohm plate impedance and 300 volts to the 4 to 16 ohm speaker impedance and remove the high voltage. If you can tell us what you want the transformer for we could help you better.
