DigiKey does not currently carry Supco SXT106 24V 40VA transformer. A possible replacement would be 237-1244-ND from Triad Magnetics. Please review the datasheet before ordering to verify it will work for your exact application as there may be some differences.
Original Supco SXT106
Source - https://www.supco.com/web/supco_live/products/SXT106.html
Suggested Replacement Triad Magnetics 237-1244-ND
Drawing:
Summary
50/60hz
50/60 hz
120 208 240