We often go thru Little Rock I-30/440/40 on our way to/from Indiana, and -you're correct- there's few choices south of town.
Have never stayed overnight in LR, but do keep a few places on our travel list (in case of emergency, etc).
Downtown Riverside RV, which Earl already mentioned
Willow Beach [COE Campground] Scott, AR -Little Rock area
Open all year, 21 sites (W/E), 30/50 amp, dump station, 60 ft max, pet friendly.
11692 Willow Beach Park Scott, AR 72142 Phone: 501-961-1332
http://www.arkansas.com/attractions/....aspx?id=94045
I-30 RV Park (Benton, AR) which you've probably already found.
http://www.i30rvpark.com
JBs RV Park & C/G (Benton, AR) too far south? I-30 at Exit 106
FHU's, 30/50 amp, pull-thru's, dump station, pet friendly.
http://www.jbsrvpark.com
Hope this helps,
Terri, the Chevy co-pilot