The profile of the channel used on original Trillium
screens may not be available any more new, there's a tab running along the edge that holds the screen on. Real pain to use btw, newer screens just use a strip spring that holds the screen in the window channel.
If you're not hooked up with second hand bs stores and are ok with white or bronze color framework , you can buy kits at home hardware stores to build your own screens from scratch start to finish.
Do make sure that the thickness of the screen channel matches that on the window itself, some may be thicker so of course won't fit.