Jon, everyone has covered the various options but little said about pro & con of each, so here is a quick run-down:
Airfix 1/72: Most accurate SeaSprite kit available with excellent detail, even a decent interior. Builds into a nice replica out of the box. A few aftermarket (AM) decals may still be available (Starfighter Decals produced a 1/48 sheet, Microscale (SuperScale now) did a 1/72 scale sheet if you can find them - all are currently out of production.) Can be found either in Airfix or MPC boxings.
Fujimi 1/72: Okay, but has inaccuracies and somewhat crude details. Good fitting kit, however.
Matchbox (now Revell) 1/48: Since I build 1/48 this is my first choice. Basic shapes okay, but lacking a lot of details. Good starting point for a build but only problem is - the landing gear *really* needs to be replaced. Since there isn't an afternarket replacement as of yet, you have to scratch build it. Excellent resin AM from 'Cobra Company' is/was available for both interior and exterior details (I collaborated with the CC guys in the production of these sets and can say, they did a great job.) The Cobra sets are still available through their website.
I am currently working up drawings of the landing gear & wheels to support either Scale Aircraft Conversions (SAC) creating masters, or making my own masters to pass on to them for production. However, latest word is that KittyHawk is going after an SH-2G in 1/48 so keep your figures crossed!
Regards, Robert