Look for RV patio mats, which are made of very light
woven polypropylene. Dirt and rain pass through.
Most common size is 9x12, which will be rather large for a Scamp-sized trailer. 6x9 is also widely available and would be my choice for a smaller trailer (check the length and projection of your awning
if you have one). The may be other less common in-between sizes.
Indoor/outdoor carpet is another thing altogether and intended for covered decks and patios.