I think you will find any safe hand loaded on to an aircraft, may only be for use on that particular aircraft..... eg an expiring MEL or not able to get out of next port with that defect.
Any other item placed on board must be covered by an authority.. usually an EOR, or stores release else its a customs breach.... so be careful !!!
There is a lot of regs about classification and packaging especially when its considered a dangerous good.
As for certifying.. I think as a general rule, dont put pen to paper unless you are covered for that type on EQ (ie ENG or A/F or T/A or E/I/R)
Just my 2 bobs worth.....
Cheers