As was said by others.. get a good memory card. I don't know where you are so I can't suggest a store, but I use the red-and-grey SanDisk 32GB microSDHC card, and it has never ever let me down.
For antennas, I have always used the Diamond SRH-789 antenna which has a hinge in it (for positioning it whichever way you desire) as well as a telescoping segment to let you "tune" it. Mine are currently several years old and feeling their age - I've broken a couple just below the hinge. The SRH-789 has the SMA connection; the RH-789 (no S) is a BNC version which you could use with the BNC to SMA adapter, if you choose.
Other than that I don't have accessories, unless you count the batteries. I use the black and silver Sanyo eneloop XX batteries and charge them in a Powerex MAHA charger, outside of the radio. The batteries last me about a regular workday (10-18 hours), and you will get better range from them if you plug the radio into a power source during the day. At my desk at work I have a spare powered USB hub, and that powers the scanner - and I can plug the hub into my laptop in order to program the scanner. It will power off virtually anything - PC USB port, USB hub, or any of the smartphone or tablet chargers. The only problem I've ever had was when I plugged the scanner into the USB port in my vehicle - the electronic navigation/media system completely spazzed out, nearly bricking the car stereo - apparently it didn't like whatever the radio said to it in serial mode when the media system said "hi, what are you and can I get your songlist?".
