I agree that the Seth Lovers and HB-1's are very different pickups, but honestly, I don't know of any modern alternative. Actually, I've had a variety of HB-1's and some of them seem very differnet from others. But they do have a commonality that is unique to them. Someone here (don't remember who) commented that where Seth Lovers have a hint of sweetness, HB-1s are fairly dry. Seems a fitting description
Having said all of that, they're both very musical pickups and a pleasure to play. I have Seth Lovers in my Nightbird, which might seem like heresy to some, especially when HB-1s would fit, but they work really well and I have no desire to swap them. And I am a pickup snob with a love for HB-1s