Nearly any commercial two-way radio shop should be able to sell you what you want.
Shreveport Communications Motorola Two-Way Radio, Wireless Broadband, Enterprise Mobility Channel Partner Shreveport, Louisiana is one example, but a simple Google search should bring you more choices so you can find the best price and who may have what you want in stock. Be aware that some may have limits on who or how they sell their wares to. For example, they may have minimum purchase requirements and/or a fee for each purchase (basically to eliminate their cost of processing very low cost sales). Ask before you purchase so you aren't surprised! Also be aware that commercial radio shops generally sell at MSRP or higher so expect to pay full price. They discount based on volume so small sales will be full price and include all taxes.
Another choice, if you can wait, would be the Shreveport Hamfest (
Shreveport) where you should have a good selection of venders to choose from, and many selling used antennas at lower prices to boot. Folks there are used to selling to folks that aren't purchasing 20 radios at a time and are happy to sell a single item. The web site indicates it's on Aug 12, 2017. There may be other hamfests that are close enough that's worth the drive for you, again Google searches is probably the best way to find them.
There are many places on-line that have what you want a toll-free phone call away and many can ship quickly so you will have what you want in just a couple of days. Often if you order early enough (2 PM is generally standard, but check to be sure) they can ship the same day so you eliminate that extra day of waiting. Shipping of something as small and light as an HT antenna will often be less than what you'll save by not having to pay sales tax, if the seller is allowed to not charge it on your sale.