Just in case anyone else comes across this problem, this is how I resolved it:

Find the default language tab id from the Tabs table by querying on PortalId and either TabName or TabPath.

Then querying the Tabs table to find the localized tab id by matching the LocalizedVersionGuid field to the LocalizedVersionGuid id from the default language tabs record and limiting the CultureCode field to the current culture code, which can be found with: System.Threading.Thread.CurrentThread.CurrentCulture.ToString()

Once you have the localized TabId, you can get the URL with: string url = DotNetNuke.Common.Globals.NavigateURL(TabId, False);