Good luck on that one Keith. When i pretzeled my 110 brake arm in 2017. I looked everywhere for just a brake arm.
I never found one, and not for lack of trying. All I wanted was the flippin brake arm.
Maybe searching Ebay which I did not do. Instead I put Bezos on the job.
For $28, I got a rebuild kit everything but the hub. Brake arm, shoes, actuator, bearings. All packed in Moly grease.
What I did not do and should have done was contact Shimano directly. My seller was BikeSomeWhere.com
Their reviews are iffy. But if might be their clientele.
I am making a two piece brake arm anchor fitting a Flyer 80 chain stay from 6061, replacing the 2mm double bolt strap.
Was nothing wrong with my shop made strap, it just was not perfect.
Tom