I see you are running a Group 31 AGM paired with a BCDC which has the solar capacity (so whatever solar solution you go for, you do not need to get a charge controller). Do you have a roof top tent on the trailer? I see a couple of options for you. Option one is to simply mount a flexible panel on your Roof top tent if you have a hard shell style tent. You should be able to pick up a 100 Watt panel, along with the wiring for about $200 and it should suffice though don't expect to get more than 3 or so Amps out of it given it will be mounted permanently and won't be movable. Alternatively, you can get yourself a folding suitcase like panel, or a lighter folding system both of which can be had for a similar price. Here are a couple of options to consider:
Renogy 100W Expandable Solar Suitcase allows for turning sunlight into usable electricity that can power your portable gears on the go. Free Shipping. Call or Order online today!
www.renogy.com
These should provide better charging because they can be angled towards the sun, but the drawback obviously is that they can't charge your battery when you are on the go (but the DC-DC charging should take care of that given your loads). With what you've described as your load, and the bank size, I don't think you need anything larger than a 100 W panel unless you want to run something like a fridge in the future.