Well I watch things on a site called 'project free tv' type that in on google and click on it then you can watch pretty much any show ever created (I haven't found anything I can't watch on there yet) then go and find himym and click on it then you can select the series you want and it will come up with a few links for each episode, if you scroll down to the bottom you should find the series finale and click on the top link for that episode it will usually be the best one for that episode (in my experience the best ones are putlocker or sockshare but it really depends)
I really hope this helps you :) xx
I don't know if this link will work but I'll give it a go
link
This is a link to the page on series 7 just scroll to the bottom ad find the best link again I hope this helps :) xx
