Most gates on stock joysticks are square, with the Sanwa Denshi square gate as the default.  While the Sanwa Denshi gate is the standard gate of choice, here is another alternative, which fits all the Sanwa Denshi JLF's (minus their Silent Series). 

So why choose the Sanwa Denshi

As noted in the product title, this fits the following joysticks:

• Qanba branded joysticks found in their Q2 and Crystal Fight Sticks
  
• Sanwa Denshi JLF Series (non-silent) Models Include: JLF-TP-8YT-SK, JLF-TP-8S-SK
  

The length and width of this unit perfectly fits Sanwa Denshi's JLF-TP-8YT-SK metal plate.

Sample image of circle gate with Sanwa Denshi JLF-TP-8YT-SK joystick (not included).