Can my CT5 be converted to use a box starter, like the CT4 ??

Both CT4 and CT5 can be used on a starter box. A none pull start backplate is not available for the NX-15 motor so starter box is the way to go if you dislike pull starter.

thanks, I am going with the box starter

where can i get a starter box?

I know Mugen and OFNA both make a starter box. You can start with those companys.