pretty much all trad dealers sell 75 & 100 grain glue on adaptors. AFA the fletch...if you need the opposite that they come with, strip them off (razor knife held flat against the shaft).
also..to remove the aluminum inserts already glued into the shafts...what you need to do is screw in a field point you don't mind loosing to mares or heat. then heat ONLY the field point with a torch (I use the burner on my gas stove)...the I hold the shaft with something non slip (like the underside of a mouse pad - same pad I use for applying wraps), grab the field point with pliers or vise grips and pull....
gotta be careful no to apply the flame directly to the shaft, and not to indirectly heat the shaft too much. then once the inserts are removed and shafts are cool....you gotta sand paper the inside of the shaft to smooth out any residual glue... and clean the inside out before gluing in your new inserts in....