My x5 had the hitch when I bought it but if I am understanding your question right you are correct. There is no replacement insert. There really isn't even much room around the hitch as is.

BTW. I don't know when my hitch was installed on my 2004 build x5 but I know that when I picked the vehicle up last month the exposed portion of the hitch was missing most of the paint and had a good layer of surface rust. This sounds weird but you may want to consider prepping this portion of the hitch and spraying on a few coats of rustoleum's industrial enamel. Its probably inevitable anyways as it is impossible to keep paint on a hitch from chipping but it can't really hurt to add more paint. I pulled my bumper and gave it a few coats - not a big deal.