I forget size but we're happy with one we got from Ace hardware. Flat top so toss stuff on top of it books, drinks, etc I keep it beside chair. But small enough that I can put in sink. Picked up 2 of these (link below) to make sure moisture levels are OK. Such as in closets or way up front. Ours has a threaded plastic port I attach a hose to and drain outside when we had RV storage/campspot away from house. At house I drain and check RV once a week. But when you first start using dehumidifier it takes awhile to get RV's dry'd out, you'll be surprised how much water you get out of it first couple times. Actual dehumidifier has gauge, but little ones make sure entire RV is good. All my drawers, cabinets cracked, so no trapped air.
https://www.amazon.com/dp/B004167OY4/ref=asc_df_B004167OY45418653/?tag=hyprod-20&creative=395033&creativeASIN=B004167OY4&linkCode=df0&hvadid=198061059251&hvpos=1o1&hvnetw=g&hvrand=9656109757246692218&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9033330&hvtargid=pla-373712639447available from cigarland in Georgetown (Seattle) or order online. Always within 1 or 2 % from national weather service. I strive for mid 50's.