EICAR like antivirus test for Windows 64 bits
Solution 1:
The purpose of the EICAR file is to identify whether your anti virus is able to detect the file entering your system, which is the exact place where your anti virus should stop the file and not at a later point. If it blocks it there it will prevent execution as well unless you manually configured your anti virus to do something different. So, EICAR works on 64 bit and you are unlikely to need an alternative test file.
Another thing with 64 bit is that a lot of viruses fail to execute because they don't apply to 64 bit code. ;)