Hopefully someone else will find this helpful.
I dug through Timken's bearing catalog to find all of their 4x100 wheel bearings - bolt on or otherwise.
I pulled application and boiled down major features that are relevant to us for the bolt-on hubs.
Code:
Part # Application & Features
512000 Saturn SC/SL/SW rear bolt-on assembly
512002 same part as above with ABS
512018 Geo prizm/corolla rear bolt-on assembly
512019 same as above with ABS
512171 geo storm bolt-on rear assembly - EXPENSIVE
512184 geo prizm/corolla rear bolt-on assembly ABS
513226 02-09 mini front bolt-on assembly
HA590063 00-06 prius rear bolt-on assembly ABS - expensive
HA590066 cobalt rear - aluminum hat - light bolt-on assembly
HA590067 same as above no ABS
HA590068 cobalt front - driven aluminum bolt-on assembly ABS very light relatively
HA590069 same as above no ABS
HA590161 02-09 mini rear bolt-on assembly
HA590170 Yaris rear bolt-on assembly
HA590172 yaris rear non ABS bolt-on assembly
HA590184 hyundai accent 07-10 rear bolt-in assembly
HA592410 Toyota echo rear bolt-in assembly looks light for bolt-in
HA594245 scion xa & echo ABS rear bolt-in assembly
HA595017 00-05 MR2 front ABS bolt-in assembly - pretty spendy
Without actually measuring weights I believe the cobalt front & rear (one of the very few driven & undriven bolt-on combos) units will be the lowest weight units - the hubs are aluminum and the majority of the rest are steel.
The other unit of interest is the front driven unit from the mini - it supposedly (again, I've only read it, haven't tested in person) accepts the outer miata CV joint making it a great option for a bolt-on rear hub if you're employing the miata drivetrain.