Can't find rear sight mount for buckmark Hi Viz fiber optic

[a1bigtuna]

I have a Buckmark with a metal rear sight mount and have a HiViz fiber optic sight but it is the long sight and it covers the rear screw so I can not remove it unless I push the drift pin out. I have heard there is a long plastic rear sight mount that will fit the long sight, but it is supposed to crack. So, do I have to just buy another fiber optic rear sight that is short or does someone out there know what I can buy, and where to buy it? Earlier I got some information, but not how to obtain a mount with a longer place for the sight and allow access for the screw.