Quoted from RobT:How hard is it to get a new backglass for something like that Top Card?
http://www.flippers.com/back4sal.html has a NOS for $250 - $450. The glass might cost you more than the whole game
BGResto http://bgresto.com/ might be able to do a resto of it for around $250.
Shay http://shayarcadegroup.com/ and Ron Webb http://pinballglass.homestead.com/don't have that glass on their list. They both sell reproduction screened glass like the originals that were used in the games.