While using a Sora with a 36t cog may not be "approved" by Shimano, it's at least worth trying. The real problem is getting clearance on the large cog, not the capacity of the derailleur.
This clearance is generally adjusted using the B screw derailleur adjustment.
If you are not able to use current derailleur with it's maximum B screw setting,
what you can try is getting a longer version of that B screw and putting the
derailluer even farther out. As a temporary hack to see if this is worthwhile,
you can put a small spacer in between the end of the B screw and the spot where
it rests on the derailluer hanger cage.
This will at least let you know if it is possible.
I am reasonably sure that if the derailleur can work with a 32t cog, you can probably tweak it enough to work with a 36t cog. If you absolutely can't make this work, then get a
"short cage" Deore MTB 9 speed derailleur. It has a long enough parallelogram and sufficent B screw adjustment to work with a 36t cog.
You don't need the long cage version of a derailleur. You just need one with a sufficiently long parallelogram.