Tiny sliding mechanism

I have been trying to build a sliding keyboard phone attachment for a while now, but can’t seem to get anywhere.

Basically, I want to combine my Moto Z Play with this cheap, generic bluetooth keyboard.

I tried double hinges, but they had too much slop. I tried a detachable fixed clamp, but that cannot be put into a pocket.

So now I am looking at making it a slider like the Motorola Droid 4 I used before.

I do have a 3D printer, so making clamps and cases/housings is no problem.

But printing a sliding mechanism will probably not result in anything remotely durable.

So my question is, what kind of sliding mechanism could I use for the sliding motion? The requirements are as follows:

• It needs to be tiny. There is really not a lot of space to waste here.
• It needs to be passably durable. As long as the parts are not too hard to get I don’t mind having to repair it once a year or so.
• It needs to cope well with dust, since I am planning on carrying that around in a trouser pocket like a normal phone.
• Low sliding resistance is very optional. A higher resistance wouldn’t be bad at all.

I looked at linear rails, but those are too large (especially the carriages). Also I fear that the ball bearings wouldn’t like the dust.

I figured that just bent steel profiles could do the trick, but I couldn’t find anyone who made Z profiles with that small of a middle section (I would need it to be like 3mm or so).

I am very much lacking the terminology to know what to search for.