Most of the alternatives (Mobapad, Hori Split Pad, etc.) I have found focus on giving a super ergonomic grip at the cost of usability when using it as a single joy-con, especially the left one (since many have a traditional d-pad instead of the four buttons).

Are there any good joy-con alternatives with: a) hall effect sticks (for longevity) b) usable as a single controller c) decent build quality d) ideally gyro and good rumble (?)

I would prefer something with more of a grip than the first party joy-cons, but still usable as single horizontal controllers.

edit: I found one option that might be good. The Aolion J20 (or the Nyxi Hyperion 2, which seems to be the same thing but marked up in price) has a joy-con like shape and is also very affordable, much less than first-party joy-cons. The only thing it doesn’t have according to one review is HD rumble. The review doesn’t show any signs of poor build quality, and the RGB looks pretty cool too. I might get that and try it out, and if it’s not very good, I’ll return it.