There is a place just down the road that is always selling old windows - call them antiques or junk - your call. Probably too far for you to go to examine them, but it's the kind of thing you find at yard sales and flea markets around here. You might check out the flea market at the fairgrounds in Raleigh and see if they have anything similar. Might find what you're looking for at a bargain price. It will be pretty hit or miss though. Also check CL under materials.
You can get "restoration" glass from Bendheim (bendheim.com). They offer two types, light restoration and full restoration. I have used their glass (full restoration) in three different projects and am very satisfied with what they provided. It isn't cheap but very worth it for an appropriate project.
+1 to Bendheim restoration glass. Here's their offerings at about $25-26/sq. ft. Not cheap, but if it's what you want for the project it's a good spend. They have plenty of other glass types (aka 20th century) that may work as well but you'll have to browse their site.
I don't know from personal experience but you might try stores that sell to stained glass craftsmen. My B-I-L does a lot of stained glass and I have seen some of his pieces that appear to look like old wavy glass.
I would pass on the old glass. Glass becomes brittle over the years, and impossible to cut to size. Most any glass supplier could get what you want, and cut to size.
Thanks guys; you have given me some options that I hadn't thought of or knew about.
Junquecol: I build period furniture and it really looks better if it has the period correct glass.
chris_goris: I tried a salvage co. over in Durham. It is hard to determine if the glass in old sash is wavy as it is always very dirty. I purchased 2 sash thinking they were old because they had ropes for counterweights. One was old and yes junquecol, it shattered when I tried to cut it. The other sash was new glass and probably had been replaced sometime in its' history.
Try Stained Glass Associates in Knightdale, Mike the owner is a real good guy, if he doesn't have what you're looking for he probably knows where to get it.
Wilson Glass in Wilson, NC used to carry reproduction glass. Not sure about their prices but I know it cost more than regular glass.
I have some sheets larger than what you are looking for but I am planning to use them. I'll look later today to see if I have more. If I do, it's free. They came from a 110 year old house.