well, this is the definition :

In broadcasting, a commercial bumper, ident bumper or break bumper (often shortened to bump) is a brief announcement, usually two to 15 seconds, placed between a pause in the program and its commercial break, and vice versa. The link is in reference 1.

or

(In TV bumpers are a brief announcement that takes place between the show and its commercial break). The link is in reference 2.

Well, there's no direct translation in Arabic, this term is simply not used. In Arabic we treat "tV bumpers" as if it were regular commercials, and translate both of them into إعلانات - فاصل إعلاني -

so you could use فاصل اعلاني
alone without mentioning خاص بالقناة