If you settle on one of the 'hinged' Hong Kong aftermarket tripod collars, make sure that the collar will allow your camera/lens to rotate to Portrait.
I ordered a Hong Kong special for my 100-400mm. Although not as refined and polished as the Canon original, it looks like it will service my lens just fine... except the groove in the collar where the little studs on the lens ride is not continuous through the hinge on the collar. The camera cannot rotate to 90 degrees (Portrait) because a stud hits the hinge. The Portrait position is located someplace in the middle of the hinge on the collar I ordered. Not good because I shoot a lot of Portrait oriented photos.
I finally bit the bullet and bought the Canon collar direct from Canon. Although expensive, it was less from Canon than any of the 'buy now' new ones I found on fleabay.
Oh yes the Hong Kong special seller would take it back and refund my money... but I would have to pay return shipping. The unit and packing weighs almost nothing... but shipping was about half the price I paid for the unit and more than twice the $6 +/- price of several units I saw on fleabay before selecting the collar I did.