Advice on choosing zoom lens on a CCTV camera

[Leuven]

I'm trying to wrap my head around putting together a video microscope and I'm stuck on lens choice.

So the basic setup is this: 1080p HDMI cctv camera (accepts a c-mount lens). The standard lens that comes with it is a cheap unbranded one, as pictured. It gives a working distance (lens to table) of about 130mm (80mm at full zoom).

This Chinese lens is £50. There are a ton of second-hand branded lenses on ebay and I'm sure some of them would give a much better quality for the money, but I don't know what I'm looking for.

So, what lens would you put in there if you were me? To make it ideal for the job, the Chinese one would get an 0.8X Barlow to reduce magnification and increase working distance. Depth of focus is important too, ideally min. 15mm.