I don't know which repository it from. i go to system-settings- install from repositories- all repositories- video add ons
The original stalker is a subscription based addon.There have been numerous attempts to hack the streams which are closed down very quickly. I would suggest you research the stalker addon and if you wish to subscribe then all well and good, if not forget the stalkers and find other free addons that give you what you want.There are lots out there if you search.