Shameless plug, but I recently completed a Kickstarter campaign for a new Mach3 pendant. It works as a keyboard emulator, but I made it do multiple keystrokes so it can handle those commands in Mach with a single button push.
If you can wait till the end of January, these will be for sale on Ebay for $60 shipped.
Made by hand in the USA by me. I check them all before shipment to ensure they work well, and I have had Beta test units out there for about a year now to ensure they will work well Long term.
Check the video's in the updates, how many pendants could handle being run over by a car, twice? =)
Jog It! Open source controller pendant for EMC2 and Mach3! by Jerome miles ? Kickstarter
-Jerome