IIRC the only big neck delta CRTs were early small screen Japanese stuff (14-16" IIRC), 2 surviving 1958 rectangular Westinghouse sets, and some broadcast monitors that seem to no longer exist. Finding a fat neck rectangular is going to be a tall order if you choose to do so.
You missed a good opportunity to get a tube with sweep hardware at the meet. I brought a Zenith CCII console with a good 25" delta CRT that someone landed for a buck.
You should get the right set in the second picture in this thread to put your creation in...
http://videokarma.org/showthread.php?t=266920