Oroville, Washington is the border town between North Central Washington and Osooyos, BC Canada. It's a short hop from Leavenworth (about 3 hours if memory serves). Anyway Oroville has a large retailer known as Princes. It used to be frequented a lot by Canadian shoppers because they used to accept Canadian money at par. Even today they give a better rate than the banks, but the Wal-Marts and other BigBox stores have beaten them up pricewise, so their prices no longer look attractive.
Anyway, I digress. The have an RV site behind the parking lot where you can stay for $6.97 a night. That gives you electric hookup, there's also community showers, laundromat and dumping facility. If you just need to dump, it's $2.00. If you are staying the night, it's included. The pads are gravel and there's a nice view. Spaces are not too tight, so for a night or two on the cheap, plan to stay here.