De or het attacheetje?

The correct Dutch article is:

het attacheetje

Rule Diminutives (-je, -tje, -pje): always het. See the rule

How to use attacheetje

the attacheetjehet attacheetje
this attacheetjedit attacheetje
that attacheetjedat attacheetje
our attacheetjeons attacheetje
your attacheetjejouw attacheetje
every attacheetjeelk attacheetje
which attacheetje?welk attacheetje?
a big attacheetje / the big attacheetjeeen groot attacheetje, het grote attacheetje