Bolero music is very similar to that which is used for Int'l Rumba. If there's a slight difference in the character of the music, it's in the orchestration: Bolero music will be more melodic and oozy, whereas Rumba music will have a bit more of a rhythmical punch. However, these days, the Int'l Rumbas being played are so syrupy, they're pretty much Boleros anyway. So feel free to go ahead and use them interchangeably.
According to one tempo chart I have for competitions, Bolero music is supposed to be played at 24 mpm, which is about 1-2 mpm slower than Int'l Rumba.
To hear examples of Bolero-like music, visit our music section at
https://www.ballroomdancers.com/Music/, search by dance style, and select Int'l Rumba.
Regards,
Jonathan