Hard to find much on DT410.

The support from Motorola is lame. Unable to find much out regarding firmware upgrades.

Well, you came to the right place. Welcome!
AFAIK, my site has more information and support for the DTR radios than anywhere else.

If you can’t find what you’re looking for, ask away!

Can you tell what cable to use to flash dtr410?

Same as the DTR550 and DTR650.

Any idea where I can buy that cable?
If not can you upgrade my radio, for a fee, of course?

I am happy to flash anyone’s radio for free, but you would have to pay shipping both ways, and I’m in Calgary, AB, Canada, so there’s that… Also no guarantees of course.
I don’t know of anywhere that you can buy that cable. As you’ve seen from the information on this forum, you can make your own of course (or if you know someone who’s handy with a soldering iron can make one)…
That being said, I haven’t done the DTR410, but I would assume that the flash software here will work.

I assume you want to flash your radio so you can use CPS? If so, do you already have the CPS programming cable?