You want the "canned" IR or visible eyes - if you don't get the canned type, they will short out the first time you get paint/liquid on them.
This was a VERY common issue with the original electronics and cause the gun to shoot while "off" (who remembers that?), drain the battery, go full auto, and other random issues.
You can get IR in any size, but the "correct" type are the canned ones. The actual "eye" is 4.64, but the package size is standardized at 5mm, just like the original intimidators. If you can't find Quest eyes, get old Intimidator ones, they both work. Trust me