Is there any botulism risk in homemade cold brew coffee?
There's probably a near zero probability to get botulism from home brewed cold coffee if done properly (clean containers/vessels, clean fridge, cold fridge temperature...  )
As long as you keep it cold, it should be ok.
(I've not made a thorough google search)
There at least one report from 2017 of a recall for nitro cold brew; it's pretty much the only report I've seen.
Here's a report of the findings, taken from this reddit thread.
I might have missed it, but it was probably an issue with their processing.