If you want it fast, call Advanced Adapters. I needed an extra snap ring when I did my SYE install and I found that no one, including NAPAs, tractor supply or the dealer had anything close to the right size. AA sent me one for about $7 plus shipping and I got it in 2 days. Even if I'm not talking about the same snap ring, they'll probably have the one you're looking for...
'98 Sport, 5spd, 3.73, AA SYE, TW driveshaft, JKS 1.25" BL, Rokmen gas tank skid, D30 Lock Right and Alloy Seals, Cobra 75WXST