You don’t really HAVE external options if you want to avoid BD riplock. You barely have internal options to avoid BD riplock. For that, I’d have to search. (But LG models were generally faster than Pioneer models, which sounds about right given Pioneer’s history of quality over speed.)
The only drives available (besides the special WH16NS…40?48?DUP, an internal drive) for scanning are the external Samsung BDRE drives. SE-506BB or CB. This excludes old stock of LiteOn iHBS112 family rebadged, which can be had as external drives (primarily by Plextor, Memorex, or HP, though eHBUx12-brandes drives also existed).
As Kerry mentioned re: the Samsung SE-506CB, there’s a glitch where 2x burns on select BD media will result in a burn using a flawed 4x strategy, effectively nuking a large chunk of the disc between two recalibration points. Consistently. Burning at 4x, or burning using other media, works fine, so the drive is still worthwhile.
If you don’t care about scanning, and want a half height drive, the LG BE14 is the most widely available external option in the west. Buffalo and Pioneer offer external HH models, but I cannot vouch for their availability outside of Asia.
Oh, wait, ASUS still rebadges LG drives for their external models, so they’re an option.
For the sake of completeness: Samsung doesn’t do half height Blu-ray drives. Matshita is Matshita, so I don’t think their HH drives have been updated in quite some years to be performant. As hinted, LiteOn doesn’t do any BD hardware that we are aware of since iHBSx12 production ended, and many of their brand partners never switched to LG or Pioneer (outside of ASUS and TEAC, most every other brand was officially handed over to LiteOn for exclusive use in one way or another).
In reference to slim external drives, in addition to the Pioneer and Samsung drives, LG and ASUS offer slim external drives. I don’t know the OEM for ASUS’s slim external drives. & of course you can get a Matshita to slap into a slim enclosure, with the knowledge that you’ll probably never get any kind of major firmware update.
Now, if you REALLY want to be adventurous, if you get the BE14, you can crossflash to an internal firmware. Including the firmware from the special WH16 that DOES support scanning on BD and DVD media. Unless LG started using 2nd generation WH16 hardware in its external models already (which can be determined by dumping the firmware), there would be absolutely no issue in crossflashing (beyond voiding the warranty, probably). This extends to the ASUS or Buffalo HH external drives that happen to be LG models; they’re probably still first gen models, too.