StichZone might be a possibility.
As an alternative, you can get custom cords, rather than stoles, from
Collegiate Regalia. (I'll admit, I like the cords better. But that may just be me.) The minimum order for custom cords is 3 dozen, but since they are a lot cheaper than stoles, it might be something the whole chapter wants to go for. Or, since there are no Greek letters involved, you might be able to order "in stock" cords for another group with red and white as their colors, like
ACR,
QC or
ASA. There wouldn't be a minimum order if you did that. Just a thought, FWIW.
ETA: In one of the "Similar Threads" identified by GC, I found
this link to the Sash Company.