How do I finish this key-binding (for PageUp-Down)

[rj <rj@xxxxxxxxx>]

I'd like to change <hold-SHIFT>-<PageUp> to a simple one-keystroke for
scrolling in zsh in the terminal.  So that I only have to press <PageUp> to
scroll back.

I currently have this partial keybinding for this:

bindkey  "^[[5~"	

That's the mapping for PageUp  --  ^[[5~  --  but what word-command do
I use on the right half of this line to accurately represent the action of
holding the shift-key and then pressing the PageUp key?