According to the 2005 Monarch brochure (link here
), the toilet on the 33PBD is on the driver's side. You may (or may not) be able to see the end of the flush sprayer by looking down the toilet. Shut off the water to the toilet as you shine a flashlight down through the valve. Use a flashlight that has a wrist lanyard, and put the lanyard around your wrist.
On my 2008 HR Admiral (twin to the Monarch) bath is on the curb side and the flush pipe to the tank passed from the wet bay, up through the floor into the bathroom, under the sink to the anti-suction and check valves, then back through the floor to the tank. It entered the tank on the curb side. I suspect your coach is a mirror image of that.
The sad news is that the tank entrance and spray head may be behind a hard-to-remove plastic panel in the driver-side rear wheel well.
Other folks will be along to suggest various chemical injections into the flush line to clear the spray head. Based on my readings on iRV2, those are a better bet than pulling the spray head on your Monarch, at least for the first attempts to fix the clog.
You should confirm what assumptions are buried in the above for yourself.