Slate roof help, falling slates

I have a very large slate roof, the slates have broken away in some places which i have replaced from time to time, the problem is that one broke away from the top and missed the gutter, it fell and hit the ground right where myself and my 3 year old son had been 5 minutes before. Does anyone know where i can get some sort of guard or snow type catcher to put around the roof. any help would be appreciated.

www.klober.co.uk/product3.php?id=109
take a look.

Being a Surveyor ( and Ex-roof Slater Adv.Craft) I can say that snow guards are no good really,they have a space beneath the barrier and are not directly to the roof,the snow guard holds the snow to prevent the snow sliding down the roof slope/ to push the gutter off/therefore this allows the snow to melt.The problem with slates sliding is the slate is flat and slides directly against the roof slope,where the pace of the slate can be fast and dangerous.A lot depends on the gutter /in relation to the roof slope itself.. if the gutter is timber/battens may be fixed to the external edge of the timber gutter.The only thing you can do with plastic is to double over flashband to make the external edge higher/but the strength is low( which would also be bodging).You would be better having 3no metal brackets fabricated(try skip makers) /1.2 m long ?/ie 2no fixings into the wall and the 2'' inch /50mm metal bent over the shape of the gutter to allow a timber barrier to be used/ & creosote.You may find galv.wall plate straps long enough which may be adapted.(Sold most good builders merchants)Without seeing a photo I am blind.Good luck