I can personally attest that I have not yet seen any glo-bettas (or any glo-fish for that matter) on the shelves on either small LFS or the large franchise Pets at Home here in the UK. Then again, I have barely seen any Bettas at any pet store here in the UK, and when I do, usually no more than two or three divided up among larger community tanks with other fish (guppies, tetras ect.) The cup phenomena I think, is limited to stores in North America. All the fish here seem to be decently treated, although perhaps with the filter output a bit too strong for some of the bettas in the community tanks-tanks clean of debris or dead fish, healthy plants ect. I am actually quite impressed. It is also a lot harder to order livestock fish online here than in North America. Again I'm not sure if thats because the fish industry is a lot smaller here in Europe/UK, or if animal welfare guidelines are better enforced and kept.
I doubt I will ever acquire a glo-fish betta for the sole reason that I never cared for them when they were other species of fish...the ones I saw back in Canada looked pretty enough I suppose, when they were all lit up in their tank, but I don't personally like the artificial/decorative appeal and prefer more natural scapes more generally-for any kind of fish. I also don't like the black light-although I'm not a fan of artificial lighting much either, a blacklight can't be used to grow plants or even fully "display" the fish, only highlights the tacky fluorescent colours and cheap plastic decorations. Also, I'm not sure how it would disrupt the natural sleep cycle of the fish, especially betta, which are diurnal like us-and thus sleep at the same time as we do (at least on nights where I'm not awake with all the lights on doing homework haha-poor Sisyphus is probably as sleep deprived as me some mornings).