just as the topic says, i have two tsubas for trade that were custom made for me a few years back. cut from 1040 steel blanks, 3/16" thick and between 2 15/16 - 3" round. perfect for your nihonto, shinken or iaito (well maybe not on nihonto LOL)
. blossum tsuba on the left was made for my wife and the pebble finish tsuba on the right has a very nice earthy brown patina and was made for me 
. both were never mounted.pm if interested