On Windows 7 (at least): Try typing chgport /? and see if you have that program. If you do, chgport COM#=COM## will map a double digit port to a single digit port assuming it isn’t already in use. e.g. use mode to see what ports exist and pick a single digit one that doesn’t.
So, for example chgport COM5=COM50 when then allow type COM5: where type COM50: will fail with "The filename, directory name, or volume label syntax is incorrect."
The trick is that unless you have hardware handshaking, the data is already gone before the PC can read it. For example, I have a board the sends back a full message like “ABCDEFGHIJKLMNOPQRSTUVWXYZ” in response to a “?” and if I send echo ?>COM5: && type COM5: I get about “HIJKLMNOPQRSTUVWXYZ”. It might work ok with xon=on
This also appares to be available as change port /?