I bought a slightly damaged seat off of ebay and had them ship it directly to Sargent when I had mine made. I've had 2 of their seats now (and 1 Saddlemen seat on my R1) the Sargent seat is perfect for me.This right here. They need the pan, so plan on sourcing another seat if you need to ride the bike during the build.
I bought one for this purpose so you are welcome to borrow it while yours is rebuilt. The Sargent (my third one across bikes) is sublime. Prostate channel. Enough said.
However, butts and preferences vary. There are people on the S1000R forums who hate Sargent seats and prefer the BMW comfort seat, meanwhile I hated my comfort seat so much I went back to the OEM seat until I bought my Sargent.
If you know someone local with a Sargent seat, try it out before buying would be my recommendation (not practical where I live, but if you're in a bigger population center, it might work for you)