I have two of these:
Fotomate LP 01 2 Way Macro Focusing Rail Slider for Canon Nikon Sony Pentax DSLR | eBay
I don't remember if I bought from that particular seller. Note the auction is for ONE rail (2 way). You need two if you want x-y. Some sellers sell as pairs (4 way).
Like Mike's, I'd say the adjustment could be smoother, but they work. They come on the slooow from China of course.
You can use one rail or put the two together for x-y control. They each have a 1/4-20 female thread on the flat side. You should be able to mount any plate you have to that the same as you would to a camera. The other side has two floating 1/4-20 male screws for mounting to the camera or to the 2nd rail, if used. One of these screws is in a stationary hole, the other is in a slotted track. The larger thumb screw drives the rail, the smaller locks it down. They are about, 6.5" x 2", decent weight to them, not flimsy.
I don't use them as much as I thought, so I am glad I got inexpensive ones. Too much trouble for bugs or flowers that might be swaying in the breeze. I use flash and high aperture handheld for that. If I need a detailed picture of a small part, I'll use these.