I'm actually leaning towards rolling my own now (no I'm not building a Tardis
). Came back from Stratco and Bunnings today and the sheds seem to be somewhere in the $300 range and that's before modifications.
Maybe building something out of plywood with a corrugated zinc / iron roof. This would also let me bring the dimensions down. To clear the telescope I only need about 1.3m square x 1.6m high. The smallest sheds I've seen are around 1.6m square x 1.9m high with anything smaller being one of those weird space saving 0.8mm wide contraptions.
I'm going to investigate the cost of materials (make it out of weatherboard or ply or metal?) and also start another thread about what kind of environment these telescopes need to survive. i.e. will humidity / heat be an issue during the day when it's not in use etc.