After the two FSL 6W T5 BL lamps in my bug-zapper, will reach EOL, I plan to buy replacement lamps at Amazon USA or Amazon UK, and I don't know if Blacklight Blue lamps are as efficient as regular Blacklight lamps to attract insects?
This looks to me that BLB lamps are more common in 6W at regular BL lamps in the Amazon USA, and that there is a high chance that I would find a 6W BLB lamp from a large brand than 6W BL lamp.
Your opinions?

Well BLBs are made of Wood's glass which is transparent to both IR and UVA (and I think the upper part of UVBs to an extent). I don't know for sure about BLs, I think they use plain soda-lime glass? It's likely they have a different spectrum. But I'm sure insects would be fooled by BLB's light just as much.

I remember using a blacklight blue CFL to get moths to fly towards and land onto a large white surface to observe them and it worked perfectly. So I can only assume a BLB source will work just as fine in a bug zapper.

BLB uses wood's glass and BL use regular glass like regular fluorescent lamps. The only difference is that wood's glass absorbs almost all the visible light while still passing the IR and UVA.

Some bug zappers use one of each.

The BLB is less disturbing to humans at night, but not sure it wont mean some adverse effects long term (eyes iris stays open, so lets more of that to pass in, good thing is the lens won't focus it that much).
Maybe some BLB filters absorb some of the UV as a "collateral" (real Woods glass is for quite some time not used on fluorescents anymore due to cost and lately environmental reason, the filter lacquer layers used instead do vary in quality among different makers).

The BLB will still work but the insect catch rate will be greatly diminished.  Insects are not only attracted to UV light but also to certain visible wavelengths, which are present above all in the BL368 phosphor which tends to be most used for the better insect trap lamps.  Those visible wavelengths are not so present in the BL365 or BL350 phosphors, which tend to be more used for standard BLB and BL lamps, and as a result they do not work so well for catching insects.  That is where many of the LED insect traps fall down.  People think that if they make a pure LED 365nm spectrum and deliver same or higher irradiance as the FL lamps, it will work just as well.  The reality is that most LED insect traps have appalling catch rates, even though they might cost an order of magnitude more.  There are however of course a few LED insect traps that do work really well, from the manufacturers that better understand this and do their own insect attraction testing to properly optimise the lamps.