Plastic saddle to seatpost guide

[Kevoffthetee]

I'm in the process of setting the pug optimum up properly and have started tackling the saddle height. Problem is it's seized and the plastic rail guide that sits on top of the flat mount is broken (even before I hit the post with a hammer).

Does anyone have any idea on where I can get a replacement or is a new seat post the way forward

Thanks, Kev