You can give Glass Station a call with the dimensions. They're on the corner of Lougheed Hwy and Mary Hill Bypass:
Glass Station
1161 Kingsway Avenue, Port Coquitlam, BC V3C6K1
(604) 552-3738
Map:
http://business.superpages.ca/superm...=BC&zip=V3C6K1
That's where I get most of my glass for broken aquariums. Also, you can use a razor to cut through the silicone and scrape it off, (that's what I use... never thought about using a piano wire). Hope this helps.
Rob