www.recreation.gov has all the Corps of Engineers and BLM campgrounds. You can search by sites with hookups. They will more than likely be booked up on weekends and holidays. You can usually find sites Sun-Thurs during the week.
Some state parks offer discounts for disabled but it varies by state.
We also use Passport America (fee to join) which is half priced camping but there are many restrictions on days, dates, etc but we feel it's worth it.
If you have time to stay at one location, many commercial campgrounds have monthly rates. I use www.woodalls.com to find commercial campgrounds.
