looks like the collet you have for the drill chuck is 1/2". [or what the shaft size of the drill chuck is]
unscrew the retainer nut from the spindle shaft and the collet will be exposed. it may need a small tap to get it out of the spindle, but when it comes out, that is the style of collets you need to look for.
post a picture of it. i "may" have some of that style still around, and if i do, i'll give 'em to ya.
it's been a long time since i have seen them, and they may have been long gone, but i can at least look.