The ornamental design for a portabletoiletbowl, as shown and described.
FIG. 1 is a top front perspective view of a portable toilet bowl in a retracted configuration;
FIG. 2 is a bottom front perspective view thereof;
FIG. 3 is a top rear perspective view thereof;
FIG. 4 is a front elevational view thereof;
FIG. 5 is a rear elevational view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof;
FIG. 8 is a left side view thereof;
FIG. 9 is a right side view thereof;
FIG. 10 is a bottom rear perspective view of a portable toilet bowl in an extended configuration;
FIG. 11 is a top front perspective view thereof; and,
FIG. 12 is a left side view thereof.
The broken line showing the aircraft antenna beacon light in FIGS. 1-12 are included for the purpose of showing environmental structure and form no part of the claimed design.