What is the best sling for discreet BFing?

Bub's feeds still take about an hour each and so far I've planned all my outings so that I can be home in time for the next feed. As this is rather limiting (and often a logistical nightmare!) I'd really like to have some way I can BF discreetly in public. I do have some BF tops, but it still seems I have to expose myself a bit for the beginning/latching-on part of the process IYKWIM.

Is there a sling that will enable a discreet latch-on??? (I do have a HAB but BFing with it looks rather tricky)

Many thanks! (and I'm very sorry if this has been asked before - I have limited internet access lately and haven't time to check!)