24V dual regulated power supply
Unless you have specific requirements of isolation levels and such, any transformer will do. For almost all applications that dont include RF the deciding factors are availability, cost, and size, usually in that order. 

Make sure that the one you get has its inputs at 220VAC, and a secondary of about 19-0-19 with sufficient current rating for what you need. The 19 comes from the fact that you need atleast 25.2 on the output to give the LM3x7 room to regulate, and after rectification you end up with 1.4 times the secondary AC rating. Best to also leave a little bit of margin on top of that. Don't go too high, though, or you risk inviting a heating problem at the regulator.