I think Silver Spray's and Action Watersports' launches are the only on Silver Lake. I don't know about Action, but SS allows for paid public launching I believe. I would check their website and give them a call and find out how that all works.
Otherwise, I would suggest using the map and finding good looking lakes and then researching to see if they have lakes. Here's a reservoir I found near I-69:
County Park Launches
If you want to head more south, there are lots of lakes in the West Bloomfield and Waterford areas, as well as Rochester and the area around it has some lakes as well I believe.