I use a large Sticky Pod now:
https://miles-wide.com/product/stick...ack-camo-copy/
I too tired of the under seat bag...it got in the way of my tail light, I had to take it off to put the bike on a stand, and just looked bad. Tried the bottle cage holder thingy...it was OK but does not hold as much as the Sticky Pod and I almost always take 2 water bottles with me on rides so it didn't work out.
After the first ride I never felt the weight in my jersey pocket.