Getting recommendation letters for grad school after 10 years in tech

      Most leaders I have worked with are too far in the past or 
      will not be interested in me leaving my current   organization.

Doesn't matter. I would ask them anyway. How important your recommendations are is context dependent so you want to figure that out first and then take proportional effort to get some.

One option is to contact some research group and express your interest in volunteering some of your time. Be open about your desire to gain some experience and get a feel of what it is like to do research, and ultimately get a recommendation letter. My sister did that and it worked really well for her.

I think you need to specify more information here. What are you looking to go to grad school for? If you want to do a PhD in renaissance literature, then the answers you're looking for will look very different than if you are applying to law, medical or business school.

You might be surprised if you ask the people you work with. I'm doing a part time MS while I work, but one of my ex managers who wrote a letter for me encouraged me to go to school and leave the company and work on cool things.

Ask your managers or skip managers, many may don't mind signing their names as long as you write it.

P.S. One of the worst parts of application process.

Bought a free eBay sniping service, developed a micropayment system for it, started to charge for it (2001)

Talk to your undergrad professors. Good luck.