I notice Myers shows out of stock for this item. They are really your only chance of finding this part . I looked for years for something to substitute on my Victory six, and sorry to say there is no alternative.
What I did for years was this: I just used a starter lead directly from the terminal on the starter (under the switch pictured) under my floorboards to a 6 volt universal starter solenoid, right up to the battery with the positive lead . You will have to wire a signal to engage the solenoid like a starter floor button or dash board push button. you need 6 volts on that signal circuit. A little push button under your seat frame would be discreet. There is plenty of room under the floorboards for the solenoid to be mounted. I ran mine this way for years until I finally bought the bullet and spent the $$$ fro the bit .
Hope this help get you rolling, Tom