Hi Graham,
For a replacement reticle try this link.
http://www.astronomics.com/main/prod...roduct_id/3999
Google 'telrad reticle' and you'll find more.
Remove the battery compartment lid.
The reticle is easy to get at, remove the old one and use very small amounts of your favourite glue on each corner to attach the new one.
Cheers,
Chris