Hi there,

I'm afraid that the only possible way is through promo codes. If I am not mistaken the person who wants to buy your app in Bulk wants to give it out to patients individually correct? Not that it is a hospital or such where they could simply use the same apple ID to login and put it on all their devices.
From my experience the only solution is through promo codes unless you release the app for free and approach a different monetization model.
I would love to have some specifics to perhaps help you out a bit further, I am currently offering a one time 15 minute free call so just go there https://clarity.fm/giulianosenese/free15
and schedule a call if you need it!