Mine got a bubble - getting hold of the correct fluid & a pipette is easy - do a 'search' on this for contact info. Needless to say there is a reason for it disappearing - on mine the plastic bowl had cracked at the join - a bit of araldite worked ok but that was only a year ago so not sure how long lasting it is. The filler is the little plastic stopper at the side which pops out along with a rubber 'o' ring. I guess if your compass is a really important piece of kit for you replacement is probably the wise choice.