Custom CultureInfo class, to be used, when instantiation of CultureInfo trigger CultureNotFoundException. Only support locale-name with format xx-XX.

CustomeCultureInfo.cs

using System.Globalization;
using System.Text.RegularExpressions;

namespace CustomeCultureInfo
{
    /// <summary>
    /// Custom culture info
    /// </summary>
    public class CustomCultureInfo : CultureInfo
    {
        public CustomCultureInfo(string name) : base(GetParentCulture(name))
        {
            Name = name;
            Parent = new CultureInfo(GetParentCulture(name));
        }

        private static string GetParentCulture(string name)
        {
            return Regex.Match(name, @"^\w+-(\w+)").Groups[1].Value;
        }

        public override string Name { get; }

        public override CultureInfo Parent { get; }
    }
}