I need this so I can use it around the workshop and in the yeard as needed

That's not going to work. A 240v circuit has two hots and a ground. 120v requires a hot, neutral, and ground.

You might want to post this in the electrical section for more suggestions.

Useful for me when im working.

Here is a link that might be useful: q-see

"That's not going to work. A 240v circuit has two hots and a ground. 120v requires a hot, neutral, and ground. "

You just need to run a 4 wire cord (hot, hot, neutral, ground).

Not a big deal at all, though the extra conductor and cost of the cord is liable to negate any advantage from using 240 V.

I could imagine the need for something like this if one was using two, high-draw 120v devices. Although it might be cheaper just to buy two extension cords, which would offer more flexibility.

I was just attempting to point out that for 120v one needs a neutral and a typical 240v circuit doesn't have that. Technically, I don't think you could make such a thing, at least from stuff found at the home center. If I'm not mistaken the components need to be rated for such use and cobbling together a x gang steel box isn't going to cut it. I don't know if something like that could be hardwired into the panel. Probably be a good idea to include GFI protection as well, especially if the cord is going to be used outdoors.

Equipment like this is actually common in industrial use.

If it is going to run hand tools than you can put GFCI receptqcles at the user end.

Any number of 4-conductor cordage is available (and even 5-conductors) since it is used in 3=phase work all the time.

It does have a lower sales volume, and is often hard usage cord making it rather expensive.

The plugs and sockets alone are also expensive (with twist locks being much preferred).

Some 50 foot #10 conductor 120 V cords would likely be cheaper in the long run.