There are Singer freearm models among the vintage group: 320, 431G, at least one or two in the 500 and 600 numbers too. Elnas are mostly freearm with the odd flatbed turning up every other year or so. Berninas are mostly freearm too, from the vintage top models 530, 730 and 830, well worth going for if they have the features you need. The myriad of brands and moels is one of the reasons I know keep an open mind, I don't know them all. The lesser known brands like Phoenix, Adler, Dürkopp, are well worth a second look when they turn up. Pfaff had some nice freearm models, as well as Viking/Husqvarna, 1950s models and up.
If you worry about hemming jeans, it's not at all a problem on a flatbed, even small childrens clothes. It has mostly to do with getting used to it. The freearm has it's advantage when you make a repairs or alterations in a difficult place like a pocket, you have to sew inside a tiny opening in the lining of a jacket, in general when there's very little room to reach the seam. For most jobs I prefer my flat bed, but since it's a straight stitcher only I use my freearm zigzagger on a regular basis.