The rear sight is the easy part. The front is not going to be nearly as easy.
I noticed from the on-line photos that it appears to have a silencer attached. Now how this attaches and the wall thickness of the tube is going to be the determining factors on whether it is practical or not.
In the case of the Armada and Marauder (which I have played with), a barrel band on the tube or by an adapter that replaces the cap (see my avatar) works after a fashion. However the biggest problem with this solution is that the shroud is screwed on. The front sight makes for a very effective wrench and the tube wants to either loosen, or over tighten. This causes all kinds of point of impact shifts.
If the Hatsan shroud is actually part of the barrel, or permanently attached, and the wall thickness is sufficient, then a band can be mounted which then can hold the front sight. This will likely be a custom machined thing, as it is unlikely that the shroud is either 3/4" (0.750") or 7/8'" (0.875"). These are the only two common sizes made for clamp-on type bands. They are also rather expensive as they are designed for aperture target sights.
The other method, is you might be able to find a ramp that can be soldered on that will have a dovetail to hold a conventional sight blade. The best source, and catalog to peruse for these solutions is Brownell's. The ramps will likely need to be fitted as the shroud is not tapered and larger diameter than conventional rifle barrels, for which these are made to fit.
If the shroud is only somewhat loosely screwed on, then the solutions are only going to be partially effective, as it will want to unscrew.
