Connecting an additional 100w mobile panel to my roof mounted system

Hi guys, first post, bear with me pls Here's my problem/situation: We have two 100w panels mounted on top of our travel trailer, which use the factory installed wiring down into the pass-thru storage area. I upgraded the stock controller to a Renogy MPPT solar charge controller. Everything works great, unless we're camped at a really shady spot. I purchased a Goal Zero Boulder 100w panel, and the hope was to move it around to sunny spots if the camper roof was in the shade. It seems like I can purchase a new solar controller, plug the Boulder 100 into that, and then use like an SAE to alligator clips adaptor to the battery. However, all that stuff is expensive, plus I usually leave the battery covered. My existing Renogy solar controller only has 1 negative and 1 positive input. Is there a way I could splice into those wires, and then have an adapter or plug so I could run that new mobile panel through the existing solar controller that is already wired to the battery? Would that be safe? I hope I explained this in an understandable manner. Any help or advice is greatly appreciated! Aaron

Are your two 100w panels wired parallel or in series? (parallel gives 12 volts, series 24 volts).
Im going to guess in series bc the factory will want to use as few wires as possible to sell it.

If parallel, then you can add a 3rd panel also in parallel as long at the controller can handle the power (amps/watts).
If in series, then run the single 100w panel into a new controller and wire that to the battery or to the wires just at the battery, which electrically is the battery as long as is of sufficient gauge.

You can get cheap controllers. What are you calling "expensive" in Dollar amounts?

Many many way to connect wires. Chose your poison. Anderson plugs are very popular. A DC outlet installed on your exterior wall that is directly wired to your aux charge controller is a cleaner option.