When I got my 89 I couldn't find anything current and compatible besides the Talleys linked above and Warne 7.3 which are 1" and fit either the Premier base or a 3/8" dovetail depending on clamp rotation.
I just saw on Talley's site they're .460" dovetail. Here's the non-lever version. Don't see them economical anywhere.
Update: I found them for $108.57 from Optics Planet, shipped free with current BF discounts... Afraid Talley will stop making what has to be a very low demand item, I ordered a set.