Hi Gorteen , you can purchase them from www.toparsenal.net , I’ve got lots of bits off them over the years & they are very satisfactory to deal with .

Also , with a small bit of modification a choke key for a Mossberg 500/Maverick 88 will also work .

I hope this will be helpful to you .

Id just go to nearest gun dealer and they'll have any amount of keys to fit the chokes.Save alot of messing about on web and maybe ending up with wrong 1