Champ trannies are easy to come by, most sites like TubeDepot have'm for not too much - I doubt you'd be able to get them wound locally for less.
The alternative with low-power stuff like Champs is to use two off-the-shelf trannies, one 240 to 6 or 12 and another up from 6 or 12 to 240. You make the first one big enough to supply heater voltage as well as feed the second, while the second provides B+ only. Light weight, small space and hum free if you use toroids, but no possibility to also use tube recto.

Contact Sue Andrews at S J Andrews will cost you around R 400. Depending on the VA rating required.