Dug here is a link, i have found them good to me once so they get this link, I have a mate who i used to go spear fishing with, he had a mares i think over 20 years ago, it still works just as well now as it did back then with no replacement parts ever.
http://www.spearfishing.com.au/frame...product_id=783
Just a thought if you have kids and plan to keep the pneumatic spear loaded only a flick of the safety will arm it (you might have to double check me on this, it's been a while) but if you have a rubber gun you can load the spear but without the rubber also armed, it cannot fire.
cheers fnq