I'd like to have this! In the meantime, I use SEDE as a workaround (has several limitations).
SEDE Workarounds and their Limitations
Limitation: If you really want the review tasks (instead of just querying for flags), you have to accept that SEDE refreshes on a weekly basis, so as the week goes on, many of the results of the query will have already been reviewed, and new review tasks won't show up until the next refresh.
Limitation: I'm not aware of any way to query for review tasks or close votes by a specific CloseAsOffTopicReasonType (or any CloseReasonType for that matter). Only flags seem to carry that information.
Approach #1: Query for flags with the desired CloseAsOffTopicReasonTypeId, then join with ReviewTasks having the same same PostId and in the active state.
Approach #2: Just query for flags. This gives more results (I just tried and got ~1.7k for flags and 0.6k for reviews-of-flags), and doesn't seem to suffer as much from becoming outdated throughout the week (not sure exactly why the number difference. My guess for the activity/SEDE-outdatedness-rate difference is because review tasks are more visible to people who like to do this sort of thing, and because review queues give badges).