Hi pepsiandcoke,
I've added a cross section of the chamber and modifications - hope this is clear.
If you could find a suitable bent pipe to insert in the side pipe then that would work but your chances of finding the right size and shape are remote. You would also have to find a way of fixing it permanently or it may fall out and block your drains.
You must thoroughly chisel the old haunching to remove soap residues and use a strong cement/fine sharp sand mix.
Regards S