The 460/k98 as the same one . on the chambers website is states the 46 one was upgraded.
460/k98 part number OS038 https://www.gunspares.co.uk/products.../460-Mag--K98/
46 part number OS038 https://www.gunspares.co.uk/products/24390/46/ Rearsight unit- Upgrade OS038
Rearsight unit- Upgrade - Metal
There may be others that use it so you would have to cross reference it .
If the one you want is different then you would need to look through all the Diana parts lists to find which ones shared the same rearsight https://www.gunspares.co.uk/categori...DianaOriginal/
OS038 rear sight here from a model 35 http://www.airgunspares.com/store/pr...ight-Assembly/