Thanks everyone for their replies. After seeing a couple people
mention the Japanese Lee Valley chisels, I ordered the set of four
yesterday at lunchtime (1/4, 5/16, 3/8, 1/2). I also added the package
of two sharpening cones in case I find that's easier than using the one
permanently attached to the machine. Once I get those I can determine
whether the super tight fit was due to the original chisel or the
bushing, in which case, one of them is going back to Woodcraft. I may
send the original chisel back anyway as the bit was a little on the
short side, even with the chuck extension installed in the mortiser. I
was a little nervous running the machine with so little of the bit in
the jaws.

Anyone know if I have a shot of seeing my chisels by the weekend? I
haven't ordered anything from LV is several years (I think it was the
plug cutters), but they still had me on file. The confirmation email I
received yesterday said everything was in stock.

Thanks
Joe