For your machine, the more "age appropriate" would be the one with cams. They are pretty fun too. There are three sets of additional cams too - and that is where things can get spendy.
I've found a few at Antique/junk malls and they are on Ebay all the time. Search completed auctions to get a feel for what they sell for. As normal, some sellers think theirs are lined with Gold.
The very early ones are all metal and look a bit like the ruffler, then came the ones that have are small and have a black cover, then the larger ones that take the cams in the middle. Then Singer figured out how to make the needle move side to side.