I sympathize with your hunt. I once floated a similar query about some more interesting music for Christmas, for example; but was met with "why do you want to do something technically challenging for Christmas, nobody cares about that".
Are you playing something like reception/background music, or is this for a sort of everybody's-watching performance?
Here's something on Amazon. It's more suited for the background music type of scenario. I just looked up "sheet music for violin," a very generic search string, and this was one of the hits. https://www.amazon.com/Movie-Hits-Violin-Leonard-Corp/dp/1495060705/ref=sr_1_17?crid=ERLHTA5H1J31&keywords=joplin+sheet+music+for+violin&qid=1658348512&sprefix=joplin+sheet+music+for+violin%2Caps%2C81&sr=8-17
I looked inside. These are not edited at all for violin, any C instrument could play these. There are no bowings, no fingerings, no dynamics, and no articulation marks. NOTHING but notes. (Maybe why they're so cheap.) So the violinist gets to do whatever they want. Still - seems like this would fit the bill in terms of the kind of music you're looking for. You can always get "fancier" by taking things an octave up, for instance, on this or that verse or repeat.
The previews don't include piano parts. If your brother is a good pianist and the parts are on the simple side, he can jazz it up by throwing in more broken chords etc.
Here's one I've used for weddings, Puccini arias: https://www.amazon.com/Play-Puccini-Arias-Transcribed-Violin/dp/0634046349/ref=sr_1_7?crid=3T8OYGG82G98F&keywords=opera+arias+for+violin&qid=1658349303&sprefix=opera+arias+for+violin%2Caps%2C105&sr=8-7 It has a few more violin-specific edits. My accompanist is quite a good player and loves improvising so he gussies up his part.