Ebay has a few listed.
You may want to check specs, research or contact sellers regarding if the handheld comes with an antenna.
What/how will you be using it? I don't know if batteries will get you much range. You'd have to see what the batteries can do. The full 4 watts may be available only from an outlet.
Using it inside a vehicle reduces range too due to the metal of the car. If, by chance, you plan on using it in a vehicle you can certainly get a decent small mobile unit for under 100. That may leave you a few bucks for an antenna. Also keep in mind antennas need to be tuned which could also cost to buy an SWR meter (with a jumper cable).
All that said there are still some CB shops around. Those folks know a sh!t ton about this stuff. Give them a ring or a visit if it interests you.
I hope some of this info helps. If you are brand new to the hobby this all may seem like a lot of info. I felt that way. Online videos & forums help a lot. It is a great hobby.
Edit: Details.
Looks like you're missing a few things to get it up and running. I'll link what I think you'll need below, and provide the cheapest/best stuff for an entry level rig.
You'll need a 12V power supply if you plan on running it from home as a "base". Here is one on Amazon for $31.00
https://www.amazon.com/dp/B0002BA570/ref=cm_sw_r_apa_i_GjrFEb2QEDQ4W
Not being able to see the power wire end, you may need a 12V cigarette adapter. Cut the wire, connect black to black, red to red, ideally soldering them and then using a heat shrink would be best, but cheap butt-connectors and electrical tape will suffice. Here is a 12V cigarette lighter plug on Amazon for $14.00
https://www.amazon.com/dp/B0016LG0CY/ref=cm_sw_r_apa_i_dprFEbRVC4YAQ
Your antenna seems to be incomplete as well. Consider buying a new, magnetic mount antenna. It includes the coax cable and is USUALLY pre-tuned for 11M (CB radio) out of the box. You SHOULD tune all radio/antenna pairs with a SWR meter, which I will discuss/link below, but in any case, here is a magnetic mount antenna on Amazon for $28
https://www.amazon.com/dp/B008ZDBM10/ref=cm_sw_r_apa_i_CtrFEbH7PH3BS
Now that you have your power supply, working radio, and antenna all hooked up, you should confirm proper SWR so that you don't damage your radio. I won't go into all the details about what SWR is or how to go about checking, but here is a link with all of that information for you to look into;
https://www.rightchannelradios.com/blogs/installation-guides/18428275-understanding-swr
Once you've got a grip on that, consider this SWR meter on Amazon for $22
https://www.amazon.com/dp/B002KRME3C/ref=cm_sw_r_apa_i_uzrFEb3DB7KGK
I hope this information helps you. Knowing what you have and what you need can be a daunting experience, especially if you are new to the hobby. This sub is very knowledgeable, as well as countless resources online. You should have little trouble in finding the information you need.
The Uniden 510XL is a fine little rig. While being entry level as far as equipment goes, it's reliable and user friendly, and fits in places you wouldn't believe! As someone who owns 2 of them currently, I highly advise a small external speaker for better audio. They are cheap and can be found anywhere. Here's one on Amazon for $17
https://www.amazon.com/dp/B000ZIC18Q/ref=cm_sw_r_apa_i_IDrFEbRTWHVFQ
As you develop in the hobby, you will learn a lot, not only about the equipment but radio theory as well. It's a very interesting subject, and with all the information and awesome equipment out there, it should provide you with years and years of fun!
Again, hope this all helps. If you have any questions, let me know or drop another post here in r/cbradio
See you on the waves!