If it doesn’t have to be that exact colorway, Tennis Classic AC is not that difficult to obtain since they’ve been retroed every now & then. Search on eBay can get you more than 200 results now and some are still new.
If u don’t want to use eBay, you can probably consider Killshot or Drop-Types that are both available through Nike’s online store now. But they are basically life style shoes nowadays (I mean, not really made for playing sports) and I wouldn’t recommend wearing them in the gym tho.