Lots of options. You can either go stock Ride Command ($$$$$) or aftermarket (a little less $). I went with a Kenwood head unit with bluetooth and Android Auto (no CD/DVD). Problem is that is not waterproof. There are a couple splash covers out there so look around to see what you want.
(And I really hate to be one of those guys, but do a search here and on the other better site. There's lots of options out there.)
You can also find waterproof radios in two general styles. The first being a typical DIN 1 format (about 2" H x 7" W) or round radios that fit into a 3-4" hole and typically used on boats. Pyle/Lanzar makes a round radio that includes a camera/video input and can display the camera's picture on a smallish (approx. 2-3/4" display), but you must buy a separate camera to use with the radio. I don't recall seeing a waterproof DIN 1 radio that includes a camera display capability. If you don't need/want the camera display, some of the marine radios allow setup using the radio buttons, but some of the round radios use a remote control for setup, so if you lose the remote, you're screwed. I am getting ready to switch out my Planet Audio PGR35B round radio that doesn't require a remote for setup with a display capable Lanzar AQR80B that requires a remote for setup. I was concerned about needing a remote to activate the camera input display, but Lanzar support told me that if it detects a video signal, the display automatically shows the camera input.
Here are links to the Planet Audio and Lanzar round marine radios - https://smile.amazon.com/Planet-Audio-PGR35B-Compatible-Weather-Proof/dp/B00VV6YCLA/ https://smile.amazon.com/Lanzar-Waterproof-Marine-Stereo-Receiver/dp/B013ALB4VO/ - This is the Silver face unit. The AQR80B has a Black face if you can find it.
Chances are, with all of the noise in the Slingshot's open cockpit, you'll probably want to run an amp for more power to the speakers. I run the SSV Works Roll Hoop speaker enclosures and had some VersaPods, normally used in Jeeps, with 4" speakers mounted on top of the dash, but my new NASCAR Styled windshield may require the VersaPods to be replaced, so I bought some SSV Works speaker pods that mount by your feet.
Here's a pic of the dash panel I made from a small sheet of ABS or PVC to hold the round radio along with a digital Voltmeter, my AFR/Boost gauge and a small cylinder to hold a pair of glasses or a candy bar. You can also see the VersaPods on the dash cover -
I used the presentation software in Libre Office (free download) to layout the template for the dash panel. You can specify the diameter for the holes and position them so they don't interfere with each other and then print the template so the height and width are the proper lengths and then tape it to whatever material you want to use to make the panel. I attached a PDF of the template I made for the AQR80B which should print at the proper size for layout on your material. The PDF template has all measurements made from the lower left corner for easy layout if taken to a shop with a CNC cutter. I had a metal shop with a waterjet cut the first panel I tried panel from a small sheet of 1/8" aluminum. I made the second panel from a piece of ABS/PVC and used hole-saws in a drill press to cut the openings.