Where can you locate a camper's VIN number? - Expert RV Advice
Locating a Travel Trailer's VIN Number - You'll find it on the lower section of the roadside sidewall, or on the frame beneath the propane tanks, possibly on a sticker or metal plate.

RV VIN Number Search & Motorhome VIN Information - Comprehensive Vehicle Details
For Towable Recreational Vehicles (such as Travel Trailers and Fifth Wheels) - Federal Certification Label: Located at the lower left front corner (roadside) of the RV.

Are there any complimentary VIN decoders available that reveal specifications or options?
For towing or travel trailers? For travel trailers, no. You can send the VIN to the manufacturer who can provide a build sheet.