I have a similar use case where I want the broadcaster to be able to set how many bits it takes to use a certain function of my extension.
Instead of just have a text field “enter desired amount here” (which also would’ve been my choice of how to handle it) I set up a few products with some typical bit amounts like 100, 200, 250, 500 and 1000 and the streamer can choose between those,
It’s a compromise, but works rather well.