Oval chain rings for ultegra spider

[big booty]

Does anyone make oval chain rings for an ultegra crank? Having cycled most of my life with the old shimano biopace Ive upgraded to a new bike with an ultegra crankset. Properly set up the old biopace (they got the indexing wrong when they introduced it in the 80s) provides a far superior pedalling stroke so Im want to see if its possible to buy oval chain rings. Not wanting to replace the whole crankset, just the chain ring.

[P!N20]

Google: Osymetric

http://www.cyclingweekly.com/news/produ ... work-28044
https://cyclingtips.com/2012/09/osymetr ... r-miracle/

Edit: sounds like they're a bit different to Biopace, but see how you go.