I am not sure what your stack looks like, but there is a fella out in Pennsylvania that makes them. I just had a chrome stack made by him. 
Crum Equipment Company
632 Erin Road
Athens, Pa. 1880
<!-- w --><a class="postlink" href="http://www.crumequip.com">www.crumequip.com</a><!-- w -->
phone# (800) 736-6432

 His specialty is John Deere, but he did a Massey for me and I am quite sure he would do Olivers. I thought his price was reasonable and pretty quick too.
I asked if he would do Olivers for me and he said yes, but you will have to know the dimensions.
         Hope this helps,
                      Cal