where can i buy the right bulbs for the cateye twin. model HL-NC250/260.Ni-cd12v The bulbs ive found have the glass going across the front of the bulb,to stop dirt or water getting in. (I think)But they stop the lock ring from screwing on properly.Leaving a gap between the lock ring & the lamp body not sealing on tight to the rubber rings. Derek.England. Tel-07506300273