Do small 1:1 isolation transformers exist?
If you're scavenging parts, you could consider using two similar transformers such as 120:12 and then 12:120. 

Or follow the suggestion of The Photon and search for a new in-stock part- there's a 12VA "Signal" (the manufacturer) part for about USD 11. in one-off. It has a nice split-bobbin construction.