You can make a reasonable fix by using a piece of PVC tubing as a 'chock'
You will notice that there is a little clip over the smaller end of the
hatch strut.  This clip can be pried off gently and held when doing so to
prevent it's escape into the continental drift.  Now the end of the strut
can be pried off the ball pin over which it sits.  A length of 3/4" OD pvc
can be cut to fit and placed over the small rod end of the strut.  Raising
the hatch will allow you to seat the 'chock' and hold the hatch open.  When
you want to close the hatch, support the hatch near the latch, raise it
slightly and position the  chock so it now slides over the larger part of
the strut.  Works fine, lasts a long time, won't split crack or peel in
direct sunlight, has no small parts dangerous to children or other living
things.

Pix available.

pensioner