You can fairly easily convert a non autodrop regulator to be autodrop by transferring the microswitch/bracket and cam from your existing regulator. Just a bit of cutting, drilling and welding needed.
Basic steps :
1. Remove the microswitch bracket off the old regulator by drilling out the welds and weld to the replacement regulator in the same place.
2. Drill 2 holes for the cable clips and transfer the clips.
3. Drill two holes for the cam mounting bolts. Weld two lengths of studding to the holes.
4. Transfer cam from old regulator to new studs on replacement regulator
5. Trim the reaction arm of the replacement regulator to be the same length as the old regulator.
6. Drill a new mounting hole in the reaction arm
7. Punch an indent as a stop for the plastic slider in the reaction arm.
Sounds a lot when written, but it isn't difficult and can be achieved quite quickly ( welding skills being the only potential problem for most people ).
Full details on how to do it here :
You can ignore the stuff about making brackets , connectors, microswitch etc ( you already have them on the currrent regulator ). The template for drilling the cam mounting bolt holes in the correct place is attached at the end of the thread.