On my last trip to this park back in January of 2019, the brochure listed this web address. When I looked it up recently, I discovered that it no longer worked. In fact, it doesn't appear to have worked for several years. To see the old site (copyright 2010), you can use the pages the Archive.org Wayback machine captured on July 6, 2020.
I think the latest official park information might be on Facebook at https://www.facebook.com/MukosurinNP/. Please be aware of banned sunscreen ingredients (park flyer).
You can find additional information about visiting the park on the following sites (not a personal or official endorsement of these sites):