You didn't state what kind of current capacity you need. You also didn't fill in the location information in your User CP so it's impossible to guess where you are or what currency you might want to pay in. This is an international forum (since it is, after all, on the Internet). I'm in Canada so in lieu of any real information as to where you are, I'll go with Canadian dollars.
You also didn't state your budget.
Here's one from Digikey which is 115VAC => 50VAC at 5A: **broken link removed** . . .but it costs $85 CDN
And one for 0.5A: **broken link removed** at $27 CDN
If you need 75mA or less, here's one for $25 CDN: **broken link removed**
Note that Digikey is international so you may well be able to find a more local Digikey to order from if you're not in Canada. You could also try searching Newark, Mouser, or other mail-order suppliers.
Depending on what kind of power you need, what you are willing to pay, and where you are, you can probably find a transformer that fits your needs. If not you might have to go with something more like what Marc suggested.
Good luck,
Torben