As Turin says, many airlines have removed their kits from the aircraft to save weight.
I've no idea if the engine covers are free though, we have a fleet of over a hundred jets yet i've only ever seen a handful of covers.
Each aircraft we have does have a set of covers for the probes though but generally they're in the kits that have been removed to save weight!
It might look messy but some plastic sheeting with a log entry is adequate for a short period of a few days. Pitot/Static covers are a little more dodgy as they are easily missed if you use the wrong temporary covers hence brightly coloured hazard tape or the aforementioned yellow rubber gloves.
Goes without saying a log entry is made for all of these so they don't get forgotten.