I would think it is a dedicated thing for your machine and you will not find other brands, as it needs to communicate with the machine's computer system. Remember the price I gave you was the Canadian price, so yours might be different.
FYI the S16 os the same machine as the Babylock Tiara, so chances are you could use the regulator from it. It might also give you an option for a dealer closer to you that knows something about it.
Quite honestly, when I tried the machine and stitch regulator .... I loved the machine but not the stitch regulator. It seemed cumbersome to operate and quite honestly, I thought my practice work without was as good as or better than with it.
I shopped three dealers last spring ... in the end only one of them knew much about using the stitch regulator and even that one was not really promoting it. All of them were saying ... buy the machine and if you want it later, get it then.