You should join the Sprinter forum,
https://sprinter-source.com/forum/forumdisplay.php?f=10. I have a leisure travel van Unity and find the group extremely helpful on all things Sprinter RV.
I have the steel wheels with the Alcoa Chrome Simulators/Hub cap. To install you take a rubber mallet and get it fitted in with just a part sticking up/out. You whack it a few times around the edge area that's out until it pops in. There should be no gap between to Simulator and steel wheel rim. You might need to hit around the entire edge to get seated properly. You need to hit it hard and its okay because the rubber mallet won't hurt it. haven't heard of just the center raised part falling off. Only the entire Simulator/hub cap. You can get a new one on Ebay for $90,
https://www.ebay.com/itm/SPRINTER-VA...NS1tLA&vxp=mtr. Most Sprinter Owners use 2-3 SST Cable ties,
https://www.homedepot.com/p/Commerci...T-10/203531940, evenly placed to maintain balance, to secure the Simulators to the wheels as an added precaution. They also come in opaque and black. These Simulators are notorious for just popping off when driving.