Exactly.
The transformer must be rated for at least the maximum power you would expect to use plus a margin for safety. Since the VA rating defines the power, you could be very adaptable on the choice of transformer in terms of volts and current but, generally speaking, keeping the volts low (<24VAC) and the current high (probably around 3A to 5A) is safer for the user.
There would be a quite large selection available on the likes of eBay if you search.
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