Radio Shack sells a handheld CB transceiver that uses a 7.5" rubber ducky antenna. The antenna can be purchased as a replacement for $9.39 plus shipping (it’s not a stocked item). I purchased one, received and installed it and it appears to work well. I can easily get to 15’ with a good signal.
The part number is 11620937. Description is ANTENNA, RUBBER. Shipping was $2.50.
Please note that Radio Shack no longer appears to stock the female BNC bulkhead connectors that are needed to mount to the TMCC unit (the antenna, of course, has a male BNC). They should be available thru Digikey or other large distributors.