Doesn't your drill press have a swivel head?

--
Sir Benjamin Middlethwaite

If it's still too long for the swivel head, and drilling by hand isn't
accurate enough, you can make a plunge router sub-base with 2x4 blocks
screwed to it, and the blocks can be clamped to the post. Then plunge
the router (with appropriate plunge-cutting bit, or pre-drilled by hand
with a smaller diam drill bit) as far as it will go into the end of the
post. If this router hole isn't deep enough, it should serve as a
fairly effective guide for drilling deeper with a forstner bit.
I recently faced the same situation while drilling 3/4" holes into the
end of 82" long bed rails, and this router jig worked well for me.
I'll attempt a little ASCII art diagram, but feel free to let me know
if you'd like a photo or a better description. The { U } represents
your router base with a round-nose router bit, ## is your workpiece.

___{__U__}____
[_]#####[_]
#####
#####
#####

(here's another try started with a monospace font, and the "bit"
plunged into the workpiece)
___{__U__}____
[_]##U##[_]
#####
#####
#####

Hope this helps,
Andy