Does that seatpost have springs, or a quick adjustment drop?
Do you need the seatpost to have springs?
I'd remove the seatpost, and check to see if it is marked with a size, somewhere near the top of where the post goes into the seat tube.
Is it marked with 27.2? Another number?
I'd probably look for a replacement post that has a different attachment method. Many of the 2-bolt posts are zero offset. Will that work?
Also, have you been having issues with the seatpost slipping down in the seat tube?
I've ridden a road bike for most of my life. One thing I am is very careful about what I run over. Heavier bikes are more forgiving with running over stuff, but it is a good idea to "unweight" the seat when you have a big bump. So, stand up a bit and using the legs as shock absorbers.