Trying to source some DYMO compatable 30334 labels - with a "catch".

Here at work we have a DYMO Label Writer 450 Turbo connected to a specialized CNC tool pre-setter machine. We feed it DYMO 30334 sized labels (1.25" x 2.25"). For whatever reason, the roll of labels MUST have those little black timing/index marks on the back for the labels to print and the DYMO to function properly. I spent considerable time yesterday calling around to different label suppliers with no success. They all have that size of label, but none of them seem to have them with the timing/index marks.

Can anyone point me to a supplier who might have these? I/we would be very grateful.

Thanks!