The place to come to share your technical expertise, or just find out what the little springy thing is that's just pinged out of sight under the work-bench.
When I rebuilt the spare forks and installed the Ohlins front end I used OEM seals they weren't silly money and they've been faultless so no complaints from me
Like stig says. I've always used Yamaha's own. They seem to last longer. The pair I have in now must be approx 15 years old and there's no problems with them yet.
Bit of advice. Buy a good bed and a good pair of shoes, because if you aren't in one you'll be in the other.