@djackal
I just use the metal lid that came with the guten, didn't bother with a more domed type, seems to work okay.
I got the parts from a farm/dairy supply shop, plenty of them here as they use a lot of triclamp stuff for dairy so I was able to go in and measure stuff just as a double check. Although the suppliers do give very good measurements and the sizes are standard. Also cheaper via aliexpress.
I did cut a hole in the lid and I sized that so that the top of a kilner jar could fit snugly and airtight onto it. Then you can lift it off and dry hop, stir, check etc. Much easier than unclipping the lid and peering in which is a bit counterproductive.
Various ways of assembling the parts, some pictures to help you, I made the sprayer by soldering a metal garden spray adapter onto a copper tube. I have since ordered a stainless steel spray nozzle with a compression fitting but haven't bothered to install it. I would do if I had my pipework in a different arrangement so that the water sprayed down rather than along in my setup ( seen a few posts above). You would need fewer components if your Guten was smaller as I went large to small and small piping works fine. I get a boil off of 700ml per hour and no problems with DMS, also have to dial the power back to about 30 percent to keep a gentle boil.
Notice that the condenser is at an angle, achieved with a loose attachment to the lid, it's still moisture tight because of the rubber washer, it means the condensation won't run back into the kettle. The water spray generates a small venturi effect to " suck " the steam away from the kettle. Water use is about 20 litres in 90 minutes, it's warm water and so can be used for washing, garden etc.
Couple of videos here
I would much rather look into the kettle than use the kegland idea of taking off that extremely hot lid to hop through.