I have got a plasma cutter that would do a rough hole in that and then you could grind / file back to what you need. OR take it to a laser cutter.

If you measure out what you need then you can post it to me and I will cut within 10mm ish of how you and it and then you can cut back. Or some people multi drill then grind and file back. I have a mate who can get stuff lazer cut too if needed but not sure on cost.

If you are in South London you can jump on the A3 and pop down and you can use my plasma cutter as much as you like. Plasmas are under £400.

I do not know the answer to the swageing.