I used one I got from a surplus place that used to be in Shoreham for a fiver, but this was a few years ago ! From what I can remember it was to be about 1.5A heaters & 250v HT.
You can get one from Maplin part no. XP27E which fits the bill. The HT when rectified will be too much, but what I did was just pad it down with an extra stage of RC filtering to the right voltage. You can check the heater draw just by getting the data on the valves & adding it up. The beauty of this transformer is that it is only £12.99 inc VAT