They do exist, but they are hard to find (out of production). Harris had some, but it appears they've sold their last stock. Might try calling them. Or search ebay for Shimano a550 model - but be sure they are the traditional nutted version, as the a550 came in both.

Another thought for the OP: not all single-pivot sidepulls are created equal. If you have a lower-end set, you may be happy with a slightly more upscale model.