Non Dictionary Value Value Enumerable

I need to store a <string, byte[]> pair for creating zip files (I execute an asynchronous download function that returns the byte array of the file, and I get the file name from parsing the URL)

I have been using a dictionary up to this point for testing, but I knew eventually we'd need something else, as the file names are not unique.

I'm sure I'm missing something simple, but I cannot for the life of me think of an Enumerable object collection which stores a non-unique <TValue, TValue> pair.

Code Sample

public async Task<ZipFile> CreateZipFormUrls(List<string> urlList)
{
    using (var zip = new ZipFile())
    {
        var files = await ReturnFileDataAsync(urlList);
        foreach (var file in files)
        {
            var e = zip.AddEntry(file.Key, file.Value);
        }

        return zip;
    }
}

async Task<Dictionary<string, byte[]>> ReturnFileDataAsync(IEnumerable<string> urls)
{
    using (var client = new HttpClient())
    {
        var results = await Task.WhenAll(urls.Select(async url => new
        {
            Key = Path.GetFileName(url),
            Value = await client.GetByteArrayAsync(url),
        }));
        return results.ToDictionary(x => x.Key, x => x.Value);
    }
}