No small bulbs are in production today, and only two companies are still producing any flashbulbs, Bowens and Meggaflash Technologies . You can still buy flashcubes, magicubes, flipflash and flashbars in some photo shops, although these may be the last stocks available. Car boot sales, garage sales, second-hand and junk shops are all worth checking for bulbs. Ask club members if you are a member of a photographic club or society. Post a notice on your works 'for sale and wanted' board.
Flashbulbs are also for sale in the photographic newsgroups.
If you are in the UK, email me . I may have some stock for sale. I am particularly interested in specimens of bulbs not already in my collection.