Your bike has a 1 1/8th head tube, so most current fork will fit (just not tapered), the biggest issue will be getting ones with rim brake mounts, although some are still around, your frame will run upto 100mm forks with no issue (I was running a 1996 GT Bravado with 100mm Rock Shox Judys till earlier this year)
There is still some aftermarket support for Quadras, and the 21R's were the best Quadras, but they aren't that good compared to modern forks.