It's good to see you take on this challenge Mick. Some of the accessories out there are so overpriced for what they are. One example is the dovetail I made for Striker's C-11 last week (and one for myself). The cost for him to get one from the USA was $220, the cost for me to get the structural grade aluminium was $21. I made 2 of them in an afternoon. If they were to be made in a very small production run at a fair profit they could be done for less than $60 each.
One suggestion I have is piggy back camera mounts. They are way overpriced from what I've seen.
Good luck with it Mick!