FIG. 1 is a front perspective view of a new and ornamental design for a transaction printer;

FIG. 2 is a rear perspective view thereof;

FIG. 3 is a right side elevation view thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is a left side elevation view thereof;

FIG. 6 is a front elevation view thereof; and,

FIG. 7 is a rear elevation view thereof.

The broken lines in FIGS. 2 and 7 are for illustrative purposes only and form no part of the claimed design.