Hey this type of wheel is modular. There are a couple types out there but I decided between these which are all almost identical. I ended up going with the American Racing Baja's $500 for a set of 4
Americas Tire Links
Pro Comp 69 $135 Item# 72888
Pro Comp 69 Wheels | America's Tire
Dimensions: 17 x9 6-139.70 -6
MB Wheels 72 $91 Item# 63612
MB Wheels 72 Wheels | Modular Trailer Wheels | America's Tire
G-FX TR-16 $125 Item# 63215
G-FX TR-16 Wheels | America's Tire
American Racing AR172 Baja $176 Item# 60202
American Racing AR172 Baja Wheels | America's Tire
Mickey Thompson also makes a super popular model
Mickey Thompson | Classic III™ Black
I would go steel if you're going offroad, which limits your options, but aluminum is still a safe bet.