GPE had done some work on replacing these using a custom board, but my understanding is can't justify it as long as anyone is selling the originals for around the $20 to $40 mark each. Apparently the DI300 chip from Allegro is a very close substitute, but misses the mark on current capacity. I found a post from GPE indicating that he looked into getting Allegro to make a chip that would be a drop-in replacement but it would require some really deep pockets.
So, we are still stuck paying the high price per chip, and not getting anything "better" for the money. I'd much rather pay $40+ for a replacement board that had a higher capacity.
The problem has been partially eliminated by the advent of the PinScore and PinLED displays. They look mostly similar, and eliminate the HV and weird chips from the equation. It's a $200 option, but will last a long time. You also get new displays, new circuits, new boards, new cabling, less heat generation, etc...
I can sell my sys 11 display board for $25 shipped. It has one 16 digit glass still on it that I know does not work. It has a couple of those chips on it you'll have to desolder.