Are there coupler pockets available for use with the accumate couplers when switching from rapido couplers?
I do not know of any available, unless B-mann's Parts Department has them. Did B-mann ever use Accu-Mates? I know that Atlas did (and may, still). You could try Atlas' Parts Department.
Another option is the Micro-Trains, which are compatible with both Accu-Mate and the McHenry that Bachpersonn uses, these days.
As you mention Rapido, I am guessing that you want to convert some older pieces to knuckle couplers. The MT 1133 is almost universal for older Bachmann equipment. If you are using really sharp curves, 1134 has a longer shank.
Later B-mann (and some of the older) does require a different conversion, but, if you check MT's website, there is an exhaustive conversion table, there.
All and Others,
I believe ATLAS holds the patent for The ACCUMATE Couplers , ATHEARN for the McHENRY Couplers and [color=red]BACJHMANN for the E-Z MATE Couplers[/color] I found this not sure if it will be of some assistance to you .
http://mrr.trains.com/~/media/import/files/pdf/e/e/0/november.ashx
http://www.google.com/patents/US8720710
TJ