The SD's are iconic and enjoyably quiet but require frequent cleaning. Some armorers recommend cleaning after 300 rounds.
The best way to go depends on what your goals and budget are.
Sears are known at best bag for the buck since you can have multiple hosts on the same pack (be able to have 9mm, 10mm, .40S&W, 5.56, .308, 300BLK, 7.62X39 all on same sear).
Double push pin guns are the most correct to the German design if you want original but you're paying a lot of money for a single MG.
My personal opinion is that a sear is the best route. My father has a DLO pack and the nice thing about that is you just buy semi auto versions of what you want to shoot and swap in the trigger pack.
Other option would be to buy a Pre-May sample. Its cheaper than transferable and you can keep it after giving up your SOT.
Good luck with your search. There are a few examples available on Strurm.