There is a recently released TS 125m f7.8 Doublet that uses FPL-53 and Lanthanum elements.
https://www.teleskop-express.de/shop...--Focuser.html
They claim excellent correction and imaging suitability. And the price is pretty attractive (less than $2k AUD, before shipping and GST). It can be reduced to f6.16 using the 3" Photoline Reducer.