Any regular 3-pin encoder such as the TTC, Kailh or ALPS encoders will work, however, you must select the accurate height:

X2H,X2V2, X2, X2A : 10mm
X2H Mini, X2V2 Mini, X2 Mini, X2A Mini : 9mm
Xlite V2, : 14mm
Xlite Wired, Xlite Wireless, Xlite V2 Mini: 13mm