R. T. Nollet    Australia                                                             www.nollet.com.au  
Transformers page   there are the standard  and the round space saving Toroidal type.
We are going to stock the most common needed types soon in Toroidal type
There are a couple of people in Australia that make/sell  Toroidal transformers
www.torema.com.au   + www.tortech.com.au + www.harbach.com.au
So if you are a high volume user and need low pricing try them first.. 2 many in the chain costs...
Sizing depends on the common sense issues of course .. what are you trying to power up ?
Voltage required and the AMPS needed determine the size .. a toroidal transformer will be a lot smaller than a conventional but the std ones do the the job also.
Standard transformer manufacturers here in Australia
www.southernelectronicservices.com.au  ( I think they also do toroidal type)
www.ironcore.com.au
You like to be added here let me know if you manufacture locally no probs at all. Email me