You may find members on here who are hoarding head castings and might sell you one ....Pinky??

.... failing that, a repair is needed as I don't think a new gasket will last long at all with so little support behind the bore seal.
I'd probably do it myself if I had that problem but don't know how adventurous you are ...
In the 70's the Electricity Supply Industry (my background, I'm an Electrical Power Engineer) used to join aluminium cables using Kynal Flux and molten aluminium alloy ladled into the aluminium ferrule, all heated using propane. By the 80's the ESI was using mechanical connectors because they were quicker and safer, so cheaper. Kynal Flux fumes were not healthy to inhale on a daily basis and the odd accident involving molten metal was not usually a 'minor accident' so there were H&S issues too. Was useful when we changed as I acquired a supply of surplus Kynal Flux and alloy rods but have used them up repairing alloy wheels and other things... including a cracked piston in a race engine...
Points to be aware of are aluminium oxidizes very quickly and the oxide film prevents good fusion at the weld. The worst is removed with a wire brush, then heated, wire brushed again, and then flux inhibits the oxide forming and assists the fusion with the filler alloy. Melting point of pure aluminium is 660°C but heads are aluminium alloy with a higher melting point. Rods are available with a range of melting points ... the lower it melts the easier it is to weld without getting the head anywhere near it's melting point so pretty easy to heat the head with a butane torch to melt the rod without causing damage to the head casting. Frosts sell rods that melt at 380°C ...
www.frost.co.uk/lumiweld-kits... but combustion temperature is quite high so I would probably go for a higher melting point rod. Some useful videos are on Youtube if you enter "aluminium welding", have a look... then, if you don't want to fix it yourself, at least you'll know what to expect of the welding shop who'll do it for you and they won't be able to 'bullshit you'... quite so much

If you do it yourself - avoid breathing the fumes ...