It seems the natural choice for a cvx to cv5 conversion would be to re-save various versions of Canvas drawing, one of them being version 5. The latest versions of Canvas should be able to work with both .cvx and .cn5 files just fine and can transform to another and vice versa.
Unfortunately, we do not know about any other program that can be used to convert cvx to cn5, so using Canvas remains your only viable choice.