I don't think there is. I looked briefly last night and didn't see anything like that.
You could, of course, modify the source code and build a version that uses larger fonts, but I don't recommend it.
What I do recommend is bringing this up on the BOINC forums. Don't forget that SETI@Home started in the late '90s and therefore many of the SETI developers and also many of the BOINC developers are almost 20 years older than when they started this, so I can pretty much guarantee yours aren't the only old eyes dealing with this problem!
It might be a feature they would build into a future release.
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