More info, like your RV type and size, style of camping enjoyed, fishing, etc, would be helpful. Looked at your blog, and looks like you may be more into dispersed than campgrounds.
East side has lots of NF campgrounds, and dispersed sites. North of Wintrop along the Chewuch River are many NF sites and open camping. West of Tonasket there are plenty of forest sites and fishing sites (Discover Pass may be needed). East of Chesaw there is a very nice, quiet spot at Beth Lake NF CG. Consider going further east to the Lake Roosevelt area and the Nat Rec Area.
Just some quick thoughts!!