Measure the screw holes and check them against other ears. They might be a fairly common pattern.

Also make sure that the ears will properly support the weight of the UPS. Lead-acid batteries are hefty. I can't tell from a quick search how it's supposed to be set up. It might need ears front and back. Or, you might find full rails.

If all else fails, get a rack shelf and just let it sit on it. Or get some scrap wood and/or steel and fabricate something.

However everything I’m finding is listed as intended for switches/routers

They reuse the same casing.

You can check the pattern, but those ears should mount just fine on it.

I just did a quick search on the model and looked at the first spec sheet that popped up, so not sure my info is correct, but its says it's 1U and about 50lbs. That seems like it's pushing the ability to use front ears alone. I saw something that mentioned a lot that came with adjustable depth rails, not ears. But again could be a slightly different model or different battery configuration or something.

Anyway, I've seen 2U ears rated for like 60lbs or so. And those are sometimes pushing it IMHO. But 1U at 50lbs would have to be extra thick and hardened to stand the torque with how narrow they'd be just based on some head physics/math, but I could be wrong.

But anyway of use use something not rated for it you might get away with it for a bit, but it would likely be really fatigued over time, especially as the rack is, bumped, shake, or moved, not to mention in an earthquake. Of it would snap and fall onto whatever is directly under it. And if there's more than an inch or so of space there, that could be disastrous. Like what if normally you have a shelf directly under it which might be providing structural integrity to the rails to not move much. But you remove the shelf while reconfiguring, the rails flex slightly as they do, and put just enough extra torque on the ears to snap them. Now whatever was under that shelf might be a few inches lower and just that distance with 50lbs could easily destroy an unshielded component or 10. Or badly damage sheilded ones. I always think worst case whenever I'm going to exceed rated standadards even if the at may never happen. But it's definitely not unlikely.

Personally, I'd either use side rails like the original kit said it came with, a shelf rated for the weight, or possibly both front and back ears if you have a shallow depth rack that fits it.

I hate to mention really bad options, but If you're set on ears, it's possible you could find some and maybe line one or two holes and drill out any that don't line up. But make sure to take into account your compromising the weight rating if you drill. I have also seen setups with a 1U device attached to 2U ears. They attached the device at the top and then had two custom rails/beams angled up from the bottom of the ears attached where the bottom 2U device hole would have been and angled up to the rear bottom of the 1U device and somehow attached there, drilled holes and bent the ends flat or around the back I think. That gave her the additional stability to reduce the torque put on the ears when the rack moved or was bumped. Seemed like more work than it was worth, but she also had another narrow component under the UPS and these rails were positioned outside the width of that, so she didn't lose the extra 1U from the too tall ears. But I think she might have gotten a lot of stuff free or super low cost from "dumpster diving" and she did have mad skills like that.

But I don't do custom stuff like that on my own, expensive devices. Might add some extra support if something looks too wobbly but is still in spec, but I'd never compromise a support part, much less add my own part not intended for that use without some serious math I'm probably not interested in doing, LOL.

I know that's a lot and I wrote quickly and didn't have time to clean up my thoughts or double check specs, but I like to show options and consequences of choices. Usually the "right way" is more expensive initially, but saves hundreds or thousands of times as much money over the "wrong way" failing. 🙂

So find verified specs for the device, or just measure and weigh it on a bathroom scale. Then find similar parts and see what they're rated for and don't use parts for 2U on 1U thst doesn't give you the support or rating listed since your attachment footprint is only half on the device, unless you're confident enough in your metalworking skills, geometry and materials science to do what "that girl" did with the support beams, lol.