i'd say the 'cheap' arai lids are probably still great - fair point - unfair remark by me (that said i wouldn't wear one - i payed the extra money myself and bought a top of the range one - and i'm not loaded or anything - just made a decision that i'd buy the best helmet i could afford).
as for the shatter proof goggles, hmmmm - i've actually been stopped at traffic lights beside garda motorcyclists and would clearly see that they were wearing standard type sun glasses in summer.
granted, it would be impractical to drive at night with a tinted visor - hence they take about 5 seconds to change and gardai have panniers on their bikes - surely they could carry around a spare visor if they wanted? or at least be given the option, should they chose to do so?
plus, i dont think that many garda bikes are around at night time anyway are they?
as for wearing normal glasses, sorry dont know!! as the other person said though - there's probably shatter proof type things available.