I have a MDR 300-C PRO, the dops I found to be as close as the OEM dops are Polymetric. These dops are a little longer than the MDR but if needed you can shorten, they also have the vee groove. I also use the Polymetric transfer jig opposed to the MDR. Contact Zane via their website http://www.polymetricinc.com
the original MDR i think is gone(out of buisness) if not let me know. i have two one very old and one master when they were last made. i know theres a fellow in california making and sell a machine as a MDR. send me a picture of your dop– the grove and its alignment with the V dop for emerald cuts and it might be possible i can make what you want. need measurements. i’m NOT pricey. regular 1/4″ by 2″ are not a problem and i make them in aluminum and brass.