As a fairly simple build the Revell (ex Matchbox) Dauphin 2 comes with USCG decals, it isn't completely accurate as an HH-65 OOB but its not bad if you are not too fussy. With a little work you can correct it (need to close up some windows, add a winch and a few other things).

In 1/48 Trumpeter also does a Dauphin 2 with USCG decals, it has similar issues to the Revell kit.

Hobbyboss has recently released a 1/72 HH-60J Jayhawk. It is supposed to be decent but the resin conversion listed below includes more detail.

Cobra Company and Fireball Modelworks have resin kits to convert an SH-60 into an HH-60J. Cobra has it for 1/48, Fireball in 1/72. 

Fireball also has a conversion to correct the Trumpeter Dauphin kit and has decals for both the HH-60 and HH-65 in both 1/48 and 1/72.

http://www.cobracompany.com/

http://www.fireballmodels.info/

There is also an Australian company that has some stuff for USCG helicopters but I can't recall the name, in addition to the HH-60 and HH-65 they have some decals and maybe resin to convert the Revell A-109 to an MH-68 and the Revell or Lindberg HH-3 kits into an HH-3F.