That's a nice looking 350x. Those rear tires look awful big though. Get that head pipe cleaned up and ceramicoated and your 350x will really stand out. As for your seat. Talk to Tammy Mosh here on the boards. She recovers seats and does a really nice job. She did a 350x seat for me, but it is a Hi Flite extra thick desert seat. She can do from stock to custom. Reasonable prices too and a quick turn around time. Check her out.
Nicholson 500x (Project)
Nicholson 185s
Nicholson 110 (That takes an atc70 tank)
Ascott 500 head/350x (Project)
Homebuilt Racer Chromoly Suspension 110 (Ragin Runt)
PK Racing Suspension 70
A+ Inc Suspension 70
AWS Aluminum 90 frame
Hi Performance ATC Suspension frame rd350
Hi Performance ATC Suspension frame 90