Here's a 2574-1 for big bucks, special order:
http://chadstoolbox.com/hazet-2574-1...djusting-tool/
And I see no reason why that 2078A tool you linked to in an ebay auction above wouldn't work, that's the correct number and looks like the right shape. Not the cheapest but not unreasonably priced. Why do you think it won't work?
In any case, if it's still available, your best bet may be to just buy the factory Volvo tool, Volvo # 9995196; if you can get it it's likely to be as cheap or cheaper than any of the aftermarket options and less of a hassle than trying to homebrew something or rolling the dice on an ebay purchase and hoping the right thing shows up in the mail. Another member was able to purchase one through Rotunda a few years back for $40. If that's still possible it's pretty well guaranteed the best deal you'll find -
http://d24t.com/showthread.php?t=707
I have both the Hazet tool and the Volvo tool, and the Hazet version is nicer, but both work identically well. I had a KD version of the VW 4cyl type that was poorly made and would slice off metal shavings when in use, so if you decide to try to make your own or modify the VW version, watch out that you don't end up doing more harm than good. This tool needs to fit and function pretty perfectly in order to be worth using and to not hurt stuff.
One more option if all else falls through, many members here have these tools, including me, and can rent or loan them...