Based on the following parts
303526: Plate 4X8 in Black
4211441: Technic Brick 1X4, Ø4,9 in Medium Stone Grey
6109934: Plate 4X4, 1/4 Circle in Bright Reddish Violet
281721: Technic Doub. Bearing Pl. 2X2 in Bright Red
This bag is from:
41105-1: Pop Star Show Stage
Brickset has a feature to allow you to search sets by tags, which is incredibley useful as you can find a full list of Polybag sets.
The list can be sorted in various ways. You can sort by year (descending) to find the newest sets that might still be available to buy, or which polybags have the most pieces and will probably be the most challenging.