Did your printrbot come with a P-block for the bed without an endstop mount? Did your printrbot come with the old style hotbed carriage without the integrated endstop mount? My original hotbed carriage stop cracked very quickly, and mine never had a y-stop. So i made these up, and tested them, and they are now on my printer.
Print these parts. NOTE you might have to file off the corner of the right x-carriage holder, otherwise the screw might hit it during printing... check clearance before printing anything.
To install y-stop, take the nut off the corner of the bed which has the y-stop microswitch on it, put the y-stop mount on the bed screw, and slide/screw it on, replace nut. Then screw an extra screw from your kit (or one of the same size) of an appropriate length into the hole, and set the y-stop position.
For the x-stop, unscrew the upper screw that attaches the hotend to the x carriage, remove the cracked/broken one the kit came with if present, and screw the new piece in, adding a screw to the hole and set the x-stop position.