Here's a list of the Sera Myu plays that were never officially recorded. Basically the only way you could have seen them is if you were in Japan at the time, or if you somehow manage to find a home video somewhere. Each of these plays took place during the first stage of the musicals, which means each one has Anza Ooyama casted as Sailor Moon. That's all we really know.

Sailor Moon - Gaiden Dark Kingdom Fukkatsu Hen (Kaiteiban) (1994 Winter Special)
Sailor Moon - Bishoujo Senshi Sailor Moon Super Spring Festival (1994 Spring Special)
Sailor Moon S - Henshin - Super Senshi e no Michi (1995 Winter Special)
Sailor Moon S - Henshin - Super Senshi e no Michi (Kaiteiban) (1995 Spring Special)
Bishoujo Senshi Sailor Moon SuperS Special Musical Show (1996 Early Summer Special)

If anyone knows of unofficial footage I'd be very interested! heart