Touratech Zega Pro and Hepco Becker are asymetrical and high quality. You would not go wrong with any of these choices.
Jesse Luggage is asymetrical, bullitproof, very highly regarded, but not waterproof. I would prefer their mounting system and would choose these if it were not for the sealing (and mebbe even so).
Happy Trails makes high quality product at affordable prices. But, it's not in the same quality class as the others. Symetrical mounting with same-size cases (mounting leaves a "hole" on the left, non-exhaust side).
SW Motech Givi Outback Trekkers are apparently symmetrical, but I'm not sure of this. There are no installation instruction given, and so I'm going by the pictures. A YouTube video here:
, at 5:50 , shows them being very close to symmetrical using the 37 / 37 L system kit, but it's not quite. It close to where you have to lok carefully.
All of these are top opening. HB makes a side opening product (the Junior model line).
Touratech Zega Pros make you relocate the turn signals. I think Jesse, Givi, and HB do not according to install instrucions. Not sure about HT.
Jesse Luggage say 78 L combined / overall size, but not individal side sizes, but likely a 33 / 45 L split.
Touratech prefers to sell ou a 31 /38 L split "system", but you can supersize it to 38 /45 L, if you order the individual parts.
Hepco Becker will sell 30, or 40 L cases (and I like the Xplorer series), but recommend the Junior Enduro series "system" (30 / 40 L split) in their notes for the side mounting rack (2015 catalog, Page 176, note "E").
SW Motech Givi Outback Trekkers will sell 37, or 48 L cases, and sell a 37 / 37 L "system" of two same-size cases. These new Outback boxes need a side rack that is not compatible with other Givi luggage.