Here's one that appears to have the firmware as downloads but you should check first - chat to the nice Chinese lady. i.e. it's your gig so your risk. RZNC-0501 - RZNC-0501,RICHNC,RichAuto - CNC Controller,RZNC-0501,RZNC-0504,RICHNC-Beijing RichNC Technology Co.,LTD

Note that the MO-CON501 is just MCPs branding. Try doing a search for just 501 CNC Pendant controller and you'll come up with all sorts of other brandings. Also - there's videos of using these things all over youtube under various brandings.

Ian