if you are looking for a ready built scale model of a modern AHTS vessel and you aren't of the well off folks who can easily spare a couple of thousands to tens of thousands of Euros for their hobby then this will really be a challenge.
The reason being simply that there is next to nothing of such ready to run (RTR) or ready to display models of this niche of modern, highly specialized work ships for sale on the market in big enough quantities to keep the price beneath a painful threshold.
The only RTR model at a bearable price that comes to my mind would be the NORDIC by Graupner
But firstly, I am not sure if this RTR model is already on sale since Gaupner (though a venerable but bankruptcy stricken German model makers kit and supplies producer and vendor) so far only anounced the advent of this model as latest addition to their Premium Line of China manufactured RTR or ARTR models. https://www.youtube.com/watch?v=QNRDl1cvBbQ
Secondly, though an undeniably attractive model of the latest and most powerful German emergency salvage tug, this is not quite what you are after, as the original isn't an anchor handling and supply tug.
The other option, that my foreposters already mentioned, would be to build your own model more or less from scratch.
Although there are even model kits like that of the AHTS FAIRMOUNT ALPINE by Billing Boats
(a Danish model kit producer and vendor which sadly also went bankrupt but whose products seem to be taken over by other vendors and at least partly on sale through them)
you have to be aware that the build of such a model, even from a kit like the above mentioned, is a long process which requires not only a sufficiently equipped workshop but also quite a few skills and a lot of patience to complete successfully.
The FAIRMOUNT ALPINE kit for instance isn't rated as being suitable for a complete novice in ship model making.
But maybe you have the skills or are adventurous and confident enough to build such a model yourself, or you have such a friend or model shipwright at hand who is willing to build it on your behalf or on commission.
In this case you could even build the FAIRMOUNT ALPINE completely from scratch (maybe at a different scale) and for instance refer to the cutting templates of body frames, stem, stern, decks and other parts of this model kit because you can download the building instructions as PDF
In the same direction of scratch building aims my third suggestion.
From FreeShipPlans you could download the plans of the 80s Polish built AHTS GRANIT
if this by today's standards somewhat veteran AHTS design meets your requirements.
But I think you still find these old work horses still being active in some offshore industry's fleets around the globe.