Cr-10 carriage needed

HELLO I have an ender 3 Pro that I installed a ender Extender 300XL kit onto. Now my 235 Ender 3 is 300 X 300. Im still using the original 235 x 235 heater which now takes forever to heat a 12" x 12" aluminum bed. I want to increase size of carriage say from a CR-10 so I can then get proper size heater with proper 300 x 300 holes in the bed. I have my eye on a 300 x 300 120v 750w keenovo heater but only if I increase carriage size. DOES ANYONE HAVE A DEAD CR-10 THEY WILLING TO PART OUT???