Essentially the seme is a celebrity or famous.
To widen results it can be a seme in position of power

Thanks

This is all I can think of right now. I didn't include rich semes, or those in positions of power, such as yakuza or princes.

Gravitation - novelist
Amayakana Toge - author
Toiki Yori mo Yasashii - novelist, but he doesn't want anyone to know who he is
Haru wo Daite Ita - they are both actors
Naisho de Alleluya - songwriter
Honenuki ni Saretai - model
Yuuwaku Sentiment, story 3 - model
Tenshi no Tamagoryouri - chef; implied he is an Iron Chef
10 Dance - both are famous dancers; we don't know which will be the seme yet

Also try searching by genre for 'Yaoi' and categories such as 'Acting', 'Modeling', Celebrity/ies', although this won't tell you which is the seme.

Thank you!