Well, regarding a list of what's been made available on VHS or DVD, all I could do is give you a list of specials I know of if you're interested in hunting them down. And the other tip I'd give you is to search for fellow forum member Justin Faulknor's profile page. Click on the "Send E-mail" link and include "Muppet Specials" in the subject heading so that he'll know what you're talking about. Ask him for any specific Muppet specials you're looking for or a list of what he has in his vast Henson productions library, come to some sort of mutual agreement as for the payment or trade of the specials, the format on which you'd like these recorded for you, and then finalize the deal amongst the two of you.
And don't forget to say that the Count sent you!
Hope this helps and have a good night.