I recall seeing nylon cable clips that might make good mounts for a spacebar stabilizer wire, but a recent extensive search came up with nothing that seemed quite suitable. However, while visiting my local hardware store, I found some 3/16" plastic low-voltage masonry stables for anchoring small cables to masonry.

- cable_clamp.png (38.73 KiB) Viewed 5697 times
These might not be as tough and slippery as nylon, but they look something like the supports for my Model M spacebar (without the nail, of course). They could be cut with a sharp knife, diagonal cutters, or dremel and then filed or sanded to make a surface for gluing to the plate.
However, to make the support more like that found in a Model M, you would need two additional pieces shaped like small-angle shims or ramps, one on each side of the overhanging piece. Someone suggested slicing the mounts out of a donor Model M and gluing them into the recipient board. It might also be possible to take a donor M to a plastics shop to have something custom made. A problem with either of these solutions is that the transplants would have some thickness at their bases, thus raising the mounts above the plane of the plate. To get around this last problem, the wire could rest directly on the plate, but little "stops" could be glued to the plate in front of the overhang.