It's listed in the PinWiki:
E-122-125
https://www.pinwiki.com/wiki/index.php/Bally/Stern#Bally
It's showing "discontinued" and "obsolete" when I Googled it. Might be difficult to find...
https://pinside.com/pinball/forum/topic/replacement-transformer-for-bally-122-125
If you don't have the patience to wait for one to pop up on eBay, you could also source out five individual transformers...
• 49 VAC
• 173 VAC
• 7.3 VAC
• 7.8 VAC
• 12 VAC
You may not find the exact output voltages, so even getting close should work.
Example: Input voltage varies 110 to 125. A transformer uses winding ratios, so if the original winding is rated 173 VAC at 115 VAC input (1.5 to 1 ratio), it's going to vary 165 to 188 VAC anyway.